Decimal Reform, the Classroom, and How People Count Today
An investigation of decimal reform initiatives, mother-tongue mathematics pedagogy, and contemporary sociolinguistic patterns in Yorùbá numeral usage.
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An investigation of decimal reform initiatives, mother-tongue mathematics pedagogy, and contemporary sociolinguistic patterns in Yorùbá numeral usage.
The Yorùbá numeral system (ònkà Yorùbá, from oní-, owner of, and kà, to count or reckon) is historically one of the most sophisticated vigesimal (base-twenty) counting systems recorded in Atlantic and Niger-Congo linguistics [S1, S8]. Across the twentieth and twenty-first centuries, the traditional system came under intense pressure from European decimal currencies, colonial and post-colonial school curricula, and global commercial practices [S6, S11]. In response, educational theorists and linguists have mounted sustained efforts either to standardize the traditional vigesimal structures for formal classroom mathematics or to replace them with regularized decimal (base-ten) coinages [S10, S11, S15]. Today, while English numerals dominate everyday commerce, broadcast media, and administrative reckoning throughout southwestern Nigeria, traditional numeral words remain resilient in sacred ritual, cowrie divination, market proverbs, and Afro-Atlantic diaspora liturgies [S8, S13, S16].
This file examines the history and evolution of the Yorùbá numeral system under modern institutional pressures, analyzes twentieth-century decimal reform proposals and the metalanguage created for school mathematics, investigates pedagogical experiments such as the Ifẹ̀ Six-Year Primary Project, details contemporary patterns of spoken code-switching, documents diasporic and ritual retention, and surveys current digital and computational implementations.
The historical trajectory of Yorùbá numeracy reflects the interplay between indigenous commercial systems, regional empire-building, Christian missionary philology, British colonial administration, and post-independence national educational policies.
In oral tradition and pre-nineteenth-century trade across the Bight of Benin, numeral reckoning was closely intertwined with cowrie shell (owó ẹyọ, the shell of Cypraea moneta) currency [S1, S3, S8]. Indigenous accounting operated on groupings of five (àrún), twenty (ogún), two hundred (igba), and twenty thousand (ọ̀kẹ́) [S1, S3]. The Ọ̀yọ́ Empire utilized these quantitative structures for imperial taxation, military levies, and market tolls across its tributary kingdoms . As documented by Samuel Johnson, tribute gathered from subject towns was calculated in standardized strings and bags of cowries, establishing a uniform vigesimal standard throughout the region .
During the nineteenth-century Yorùbá civil wars, when mass displacement reorganized populations into armed encampments such as Ìbàdàn, Abẹ́òkúta, and Ìjàyè, large-scale market transactions and military logistics maintained the vigesimal structure . Simultaneously, Liberated Africans in Freetown and Christian Missionary Society (CMS) linguists began documenting Yorùbá number words in print [S1, S2]. Samuel Ajayi Crowther published the earliest comprehensive printed lists of Yorùbá numerals in his vocabularies of 1843 and 1852 . Crowther documented the subtractive morphophonology of the language, recording forms like eérìndínlógún (sixteen, literally "four before twenty") and àádọ́ta (fifty, literally "ten before sixty") . In 1858, American Southern Baptist missionary Thomas Jefferson Bowen published a detailed grammatical sketch noting the regular cyclic alternation of addition and subtraction between decade boundaries .
In 1886, Adolphus Mann delivered a paper to the Royal Anthropological Institute in London, published in 1887 as Notes on the Numeral System of the Yoruba Nation . Writing as a colonial observer, Mann characterized the Yorùbá numeral framework as a monument of intricate mental arithmetic, comparing its subtractive architecture to Moorish ornamentation . Levi Leonard Conant subsequently discussed the system in his 1896 comparative study The Number Concept, classifying Yorùbá among the most advanced non-decimal counting systems in the world .
With the establishment of the British Southern Nigeria Protectorate and the subsequent amalgamation of Nigeria in 1914, colonial authorities introduced British imperial currency (pounds, shillings, and pence) and English-medium schooling [S6, S11]. Although British currency was non-decimal (twenty shillings to the pound, twelve pence to the shilling), colonial primary schools enforced English arithmetic, initiating a widespread diglossic split: English numbers were used for textbook calculations and administrative paperwork, while Yorùbá numbers remained in oral market exchange and domestic life [S6, S11].
Following Nigerian independence in 1960, scholars sought to reclaim indigenous languages for formal education [S6, S11]. Robert G. Armstrong published Yoruba Numerals in 1962, analyzing the mathematical consistency of the vigesimal system while noting the severe pedagogical difficulties it posed for primary pupils trained in pencil-and-paper decimal arithmetic . In 1970, the Institute of Education at the University of Ifẹ̀ (now Obafemi Awolowo University), under the leadership of Aliu Babatunde Fafunwa, launched the Ifẹ̀ Six-Year Primary Project (SYPP) . The project demonstrated that children taught mathematics and sciences entirely in Yorùbá outperformed English-medium cohorts in cognitive grasp and conceptual flexibility [S11, S12].
In 1973, Nigeria officially decimalized its national currency, replacing the Nigerian pound with the naira (divided into 100 kobo) [S10, S14]. This national monetary reform accelerated debates among Yorùbá linguists. Scholars such as Oladele Awobuluyi argued that the traditional vigesimal system, with its heavy reliance on subtraction and compounding, placed an unnecessary cognitive burden on schoolchildren and proposed a completely regularized, decimal numeral system [S10, S15]. Concurrently, the Nigerian Educational Research and Development Council (NERDC) convened national committees that produced the Yoruba Metalanguage (Èdè Ìperí Yorùbá) volumes in 1984 and 1992 under the editorship of Ayọ Bamgbọṣe, standardizing technical mathematical terminology in Yorùbá .
In the twenty-first century, Yorùbá numeral practice exhibits a sharp bifurcation [S14, S16]. In everyday urban conversation, market bargaining, radio broadcasts, and digital transactions across southwestern Nigeria, speakers overwhelmingly code-switch to English number words, particularly for quantities above ten [S14, S17]. Conversely, the traditional number words remain preserved in oral literature, Ifá divination verses, the sixteen-cowrie (ẹẹ́rìndínlógún) divinatory system, and sacred praise poetry (oríkì) [S8, S13]. Across the Atlantic, Lucumí practitioners in Cuba and Candomblé Ketu initiates in Brazil preserve the first sixteen to twenty Yorùbá number words as essential liturgical terms during divinatory casting (diloggún and jogo de búzios) [S13, S16].
+----------------------------------+-------------------------------------------------------------------------+
| Period / Date | Key Developments in Yorùbá Numeral Practice |
+----------------------------------+-------------------------------------------------------------------------+
| Pre-1800 (Precolonial / Ọ̀yọ́) | Vigesimal cowrie currency accounting; standardization under Ọ̀yọ́ Empire |
| 1843, 1852 (Crowther) | Earliest printed vocabularies documenting subtractive morphophonology |
| 1858 (Bowen) | Grammatical description of decade alternations and cyclic subtraction |
| 1887 (Mann) | First major anthropological treatise on cowrie-counting arithmetic |
| 1896 (Conant) | Comparative classification of Yorùbá vigesimal structures in ethnology |
| 1914-1960 (Colonial Era) | Imposition of British currency; English-medium primary arithmetic |
| 1962 (Armstrong) | Linguistic analysis of vigesimal structures versus decimal school needs |
| 1970-1978 (Ifẹ̀ Project / Fafunwa) | Full mother-tongue primary curriculum; math taught in Yorùbá |
| 1973 (Nigerian Currency Reform) | Introduction of decimal Naira; intensified calls for decimal counting |
| 1975, 1977 (Hurford, Ekundayo) | Generative linguistic modeling of vigesimal derivational morphology |
| 1984, 1992 (NERDC / Bamgbọṣe) | Publication of Yoruba Metalanguage (*Èdè Ìperí Yorùbá*) terminology |
| 2001 (Helen Verran) | Epistemological study of Yorùbá whole-part logic in classroom math |
| 2008-2016 (Awobuluyi) | Comprehensive decimal reform proposals published in linguistic monographs|
| Present Day | Extensive code-switching to English; survival in ritual, app engineering |
+----------------------------------+-------------------------------------------------------------------------+
The traditional Yorùbá counting framework derives complex numerals through three simultaneous mathematical operations: addition (ìròpọ̀), subtraction (àyọkúrò), and multiplication (ìsọdipúpọ̀) [S1, S7, S8].
The system uses twenty (ogún) as its primary base, ten (ẹ̀wá) as an intermediate pivot, and two hundred (igba) and four hundred (irínwó) as major multiplicative anchors [S1, S6, S8]. Between decades, units one through four are derived additively using the conjunction lé (to be in addition, to exceed):
Units five through nine are derived subtractively from the upcoming decade using the operator dín (to be less by, to reduce):
This subtractive mechanism recurs across every decade: 45 is aárùndínláàdọ́ta (five from fifty); 46 is eérìndínláàdọ́ta (four from fifty); 55 is aárùndínlọ́gọ́ta (five from sixty) [S7, S8]. Multiples of twenty beyond forty are multiplicative: ogójì (40, ogún-méjì, 20 x 2); ọgọ́ta (60, ogún-mẹ́ta, 20 x 3); ọgọ́rin (80, ogún-mẹ́rin, 20 x 4); ọgọ́rùn-ún (100, ogún-márùn-ún, 20 x 5) [S1, S6, S8]. The intermediate odd tens are subtractive: àádọ́ta (50, 60 minus 10); àádọ́rin (70, 80 minus 10); àádọ́rùn-ún (90, 100 minus 10) [S1, S6, S8].
Higher numbers operate on multiples of two hundred (igba): 300 is ọ̀ọ́dúnrún (400 minus 100); 400 is irínwó (originally erí-nwó, four hundred cowries); 2,000 is ẹgbàá (literally ẹgbẹ̀wá, ten times two hundred) [S3, S6, S8].
Early missionary and colonial orthographies transcribed these compound words with varying phonetic approximations, vowel elisions, and diacritic strategies. The table below places historical attestations alongside modern standardized orthography:
+-------+-------------------+---------------------+-------------------+-------------------+-------------------+
| Value | Modern Standard | Crowther (1852) | Bowen (1858) | Mann (1887) | Abraham (1958) |
+-------+-------------------+---------------------+-------------------+-------------------+-------------------+
| 11 | ọ̀kanlá | okanla | okanla | okanla | ọ̀kanlá |
| 15 | ẹ́ẹ́dógún | edogun | edogun | edogun | ẹ́ẹ́dógún |
| 16 | eérìndínlógún | erindinlogun | erindinlogun | erindinlogun | eérìndínlógún |
| 20 | ogún | ogun | ogun | ogun | ogún |
| 25 | eédọ́gbọ̀n | edogbọn | edogbọn | edogbon | eédọ́gbọ̀n |
| 30 | ọgbọ̀n | ogbọn | ogbọn | ogbon | ọgbọ̀n |
| 40 | ogójì | ogoji | odźi | ogodji | ogójì |
| 50 | àádọ́ta | aadota | adọta | aadota | àádọ́ta |
| 60 | ọgọ́ta | ogota | ogọta | ogota | ọgọ́ta |
| 70 | àádọ́rin | aadorin | adọrin | aadorin | àádọ́rin |
| 80 | ọgọ́rin | ogorin | ogọrin | ogorin | ọgọ́rin |
| 90 | àádọ́rùn-ún | aadorun | adọrun | aadorun | àádọ́rùn-ún |
| 100 | ọgọ́rùn-ún | ogorun | ogọrun | ogorun | ọgọ́rùn-ún |
| 200 | igba | igba | igba | igba | igba |
| 300 | ọ̀ọ́dúnrún | ọdunrun | ọdunrun | oodunrun | ọ̀ọ́dúnrún |
| 400 | irínwó | irinwo | irinwo | irinwo | irínwó |
| 2000 | ẹgbàá | ẹgba | egba | egba | ẹgbàá |
| 20000 | ọ̀kẹ́ | ọkẹ | ọkẹ | oke | ọ̀kẹ́ |
+-------+-------------------+---------------------+-------------------+-------------------+-------------------+
Sources: Crowther (1852: 32-36) ; Bowen (1858: 18-22) ; Mann (1887: 60-64) ; Abraham (1958: 462-465) . Note that Bowen records odźi for 40 alongside ogoji, representing dialectal palatalization, whereas Mann transcribes the same form as ogodji [S2, S3].
In theoretical linguistics and ethnomathematics, the complex derivation of Yorùbá numerals generated major debates in the 1970s and 1980s regarding human cognitive competence, generative grammar, and universal numeral syntax [S8, S12].
James R. Hurford, in The Linguistic Theory of Numerals (1975), devoted a key case study to Yorùbá, arguing that its numeral system presents one of the most mathematically intricate challenges to universal generative grammar . Hurford demonstrated that Yorùbá requires complex syntactic phrase-structure rules to handle overcounting, where a number is expressed by anticipating a higher base and subtracting from it before reaching it .
In 1977, S. A. Ekundayo responded in Anthropological Linguistics with a formal analysis titled "Vigesimal Numeral Derivational Morphology: Yoruba Grammatical Competence Epitomized" . Ekundayo argued against viewing the system as unnecessarily convoluted, demonstrating that native speakers master its derivational morphology effortlessly through an internalized phrase-structure grammar . Ekundayo mapped out the formal allomorphy of the system:
Ekundayo concluded that the traditional numeral system represents an apex of morphological productivity, reflecting deep mathematical symmetry rather than arbitrary irregularity .
In Science and an African Logic (2001), philosopher and educator Helen Verran documented her field experiments teaching mathematics in primary classrooms across southwestern Nigeria between 1979 and 1986 . Verran critiqued Western cognitive psychologists who had claimed that African languages lack abstract mathematical categories .
Verran identified a fundamental epistemological difference between English and Yorùbá numbering :
In a Yorùbá primary classroom, when children count bundles of sticks or heaps of seeds, they reckon them as structured configurations rather than isolated abstract dots on a number line . Verran showed that traditional classroom difficulties arose not because Yorùbá children lacked logical ability, but because colonial and post-colonial textbooks forced English set-theoretic assumptions onto pupils whose linguistic intuition operated on whole-part configurations .
+------------------------------------+-------------------------------------------------------------------------+
| Dimension | Contrast: English Set Logic vs. Traditional Yorùbá Whole-Part Logic |
+------------------------------------+-------------------------------------------------------------------------+
| Foundational Unit | Discrete, isolated individual unit (1) collected into sets |
| Primary Conceptual Base | Decimal (base-10), powers of 10 (10, 100, 1,000) |
| Intermediate Operations | Purely additive within decades (twenty-one, twenty-two) |
| Epistemic Focus (Verran 2001) | One-to-many abstraction; cardinal placement on an infinite line |
| Yorùbá Approach | Structured wholes sorted into proportional sub-heaps and bundles |
| Yorùbá Conceptual Base | Multi-base (base-5, base-10, base-20, base-200, base-20,000) |
| Yorùbá Intermediate Operations | Anticipatory overcounting; cyclic addition (1-4) and subtraction (5-9) |
| Epistemic Focus (Verran 2001) | Whole-part relational configuration; concrete-emergent materiality |
+------------------------------------+-------------------------------------------------------------------------+
Despite its mathematical symmetry, the vigesimal system presents real challenges for modern decimal mathematics, written column arithmetic, and commercial technology [S10, S15]. From the 1960s onward, a major movement emerged among Yorùbá linguists advocating for decimalization.
Linguists and educators identified four specific friction points between the traditional system and modern schooling [S10, S14, S15]:
The most prominent and systematic proposal for decimal reform was developed by Professor Oladele Awobuluyi in Ẹ̀kọ́ Ìṣẹ̀dá-Ọ̀rọ̀ Yorùbá (2008) and related publications [S10, S15]. Awobuluyi proposed discarding the vigesimal base, eliminating all subtractive formations, and adopting a strictly additive, left-to-right decimal paradigm [S10, S15].
In Awobuluyi's system, the primary decade root is ẹwá (ten). Multiples of ten are formed by compounding ẹwá with unit numerals, and intermediate numbers are formed by simple addition (lé) without subtraction [S10, S15]:
+-------+----------------------------+------------------------------+----------------------------------------+
| Value | Traditional Vigesimal Form | Awobuluyi's Proposed Decimal | Structural Breakdown of Decimal Form |
+-------+----------------------------+------------------------------+----------------------------------------+
| 15 | ẹ́ẹ́dógún (20 - 5) | ẹwá-márùn-ún | ten + five |
| 18 | eéjìdínlógún (20 - 2) | ẹwá-mẹ́jọ | ten + eight |
| 20 | ogún (base) | ẹwá-méjì (or ẹwádéjì) | ten x two |
| 25 | eédọ́gbọ̀n (30 - 5) | ẹwá-méjì-márùn-ún | ten x two + five |
| 30 | ọgbọ̀n (20 + 10) | ẹwá-mẹ́ta (or ẹwádẹ́ta) | ten x three |
| 40 | ogójì (20 x 2) | ẹwá-mẹ́rin (or ẹwádẹ́rin) | ten x four |
| 50 | àádọ́ta (60 - 10) | ẹwá-márùn-ún (or ẹwádárùn) | ten x five |
| 70 | àádọ́rin (80 - 10) | ẹwá-méje (or ẹwádéje) | ten x seven |
| 90 | àádọ́rùn-ún (100 - 10) | ẹwá-mẹ̀sán-án (or ẹwádẹ̀sán) | ten x nine |
| 98 | eéjìdínlọ́gọ́rùn-ún (100 - 2) | ẹwá-mẹ̀sán-án-mẹ́jọ | (ten x nine) + eight |
| 100 | ọgọ́rùn-ún (20 x 5) | ọgọ́rùn-ún (retained as 100) | one hundred (base 10^2) |
| 1000 | ẹgbẹ̀rún (200 x 5) | ẹgbẹ̀rún (retained as 1,000) | one thousand (base 10^3) |
| 1.0M | àádọ́ta ọ̀kẹ́ (50 x 20,000) | àadọ́kẹ́ (or mílíọ̀nù) | million (standard base 10^6) |
+-------+----------------------------+------------------------------+----------------------------------------+
Sources: Awobuluyi (2008: 45-52) ; Akerele (2023: 8-14) .
The decimal reform proposals triggered substantial debate among Yorùbá intellectuals and educationalists [S10, S15]:
In practice, Awobuluyi's decimal system has gained traction in specialized academic translation and linguistic textbooks, but it has not fully displaced traditional numerals in cultural contexts or English numerals in daily speech [S15, S17].
The most significant institutional attempt to deploy Yorùbá numerals in modern formal schooling was the Ifẹ̀ Six-Year Primary Project, supported by the standardization work of the Nigerian Educational Research and Development Council (NERDC) [S9, S11].
Conceived by Professor A. Babs Fafunwa at the University of Ifẹ̀, the Six-Year Primary Project (SYPP) was an experimental educational trial designed to test whether primary education conducted entirely in the child's mother tongue (Yorùbá) would produce superior academic and cognitive outcomes compared to traditional English-medium education .
Beginning with a pilot cohort at St. Stephen's Anglican Primary School in Modákẹ́kẹ́, Ilé-Ifẹ̀, the project developed an entire primary curriculum in Yorùbá spanning six subjects: Mathematics (Ìṣirò), Science (Ìmọ̀ Ìjìnlẹ̀), Social Studies (Ẹ̀kọ́ Àwùjọ), Yorùbá Language Arts, Physical Education, and English as a Second Language .
For mathematics instruction, curriculum developers faced the challenge of translating standard arithmetic into Yorùbá [S11, S12]. Rather than inventing an artificial decimal vocabulary, the project initially adapted traditional number words while introducing systematic terminology for operations, shapes, and measurements [S9, S11]. Comprehensive longitudinal assessments conducted between 1970 and 1976 demonstrated that pupils in the Yorùbá-medium experimental classes scored significantly higher in mathematics and general cognitive tests than control pupils taught in English . Furthermore, experimental pupils showed no deficit in English language acquisition when transitioning to secondary school .
Despite the project's success, political instability, funding limitations, and federal reluctance to mandate indigenous-language instruction nationwide prevented the Ifẹ̀ model from becoming universal policy across southwestern Nigeria .
To support mother-tongue education and media broadcasting, the NERDC sponsored national symposia of the Yoruba Studies Association of Nigeria (YSAN) to produce standardized technical lexicons . Published in two volumes as Yoruba Metalanguage (Èdè Ìperí Yorùbá), edited by Ayọ Bamgbọṣe (Vol. 1, 1984; Vol. 2, 1992), these works established an official glossary of mathematical and scientific terms :
+---------------------------+----------------------------------+----------------------------------------------+
| English Mathematical Term | Yorùbá Metalanguage Standard | Morphological Derivation |
+---------------------------+----------------------------------+----------------------------------------------+
| Arithmetic / Mathematics | Ìṣirò | Nominalization of *ṣírò* (to calculate/reckon) [S9] |
| Number / Numeral | Ònkà | *oní-* (owner of) + *kà* (to count) [S9] |
| Addition (+) | Ìròpọ̀ | Nominalization of *ró pọ̀* (to add together) [S9] |
| Subtraction (-) | Àyọkúrò | Nominalization of *yọ kúrò* (to extract from) [S9]|
| Multiplication (x) | Ìsọdipúpọ̀ | *sọ di púpọ̀* (to turn into many) [S9] |
| Division (÷) | Ìpín | Nominalization of *pín* (to divide/share) [S9]|
| Fraction | Ìdá | Nominalization of *dá* (to break/part) [S9] |
| Equation | Ìdọ́gba | Nominalization of *dọ́gba* (to be equal) [S9] |
| Decimal | Dẹ́símà (or Ìpín mẹ́wàá) | Direct loan / calque (tenth parts) [S9] |
| Percentage (%) | Ìdá ọgọ́rùn-ún | *ìdá* (part of) + *ọgọ́rùn-ún* (hundred) [S9] |
| Geometry | Jẹomẹ́tírì | Loan phonology [S9] |
| Place Value | Ipò Nọ́mbà | *ipò* (position) + *nọ́mbà* (number) [S9] |
+---------------------------+----------------------------------+----------------------------------------------+
Sources: Bamgbọṣe (1984: 45-62; 1992: 78-91) .
These coinages were incorporated into primary school curricula and teachers' colleges, establishing a functional vocabulary for discussing abstract mathematics in Yorùbá .
In everyday contemporary life across Yorùbáland (comprising Lagos, Ọ̀yọ́, Ògùn, Ọ̀ṣun, Oǹdó, Èkìtì, and parts of Kwara and Kogi states), numeral usage exhibits pronounced diglossia and code-switching [S14, S17].
Linguistic surveys of spoken Yorùbá reveal that speakers alternate between three systems depending on domain, register, and social context [S14, S17]:
+----------------------------------+----------------------------+---------------------------------------------+
| Communicative Domain | Dominant Numeral Form | Sociolinguistic Rationale |
+----------------------------------+----------------------------+---------------------------------------------+
| Market Bargaining (Under ₦100) | Yorùbá (Traditional) | Brevity of short roots (*ogún*, *ọgbọ̀n*) [S17] |
| Market Bargaining (₦500 - ₦100k+) | English digits / Pidgin | Rapid calculation, avoids large compounds [S17]|
| Bus / Transport Fares | English / Yorùbá mixed | *Fifty*, *Hundred*, *Two hundred* common [S17] |
| Stating Phone Numbers | English digits (solely) | Digit-by-digit sequencing [S14] |
| Telling Time | English / Yorùbá mixed | *Agogo méjì* (2 o'clock) vs. *Two-thirty* [S17]|
| Divination & Ritual Offerings | Traditional Vigesimal | Sacral requirement of Ifá verses [S13] |
| Radio / TV Yorùbá News | Decimalized Yorùbá Calques | NERDC standardization policy [S9] |
+----------------------------------+----------------------------+---------------------------------------------+
A study by A. A. Amuda (1994) on conversational code-switching among educated Yorùbá speakers documented that numeral citation was one of the most frequent triggers for intra-sentential language switching . Speakers embedded English numerals into otherwise grammatical Yorùbá sentences because English numerals are monosyllabic or disyllabic, whereas Yorùbá equivalents require complex morphophonological processing [S14, S17]. For example, a speaker will spontaneously say:
rather than the traditional:
Younger urban speakers in metropolitan Lagos often exhibit incomplete acquisition of the traditional vigesimal system above twenty, recognizing only isolated roots like àádọ́ta (50) and ọgọ́rùn-ún (100) while conducting all active arithmetic in English [S14, S17].
In traditional Yorùbá thought, numbers carry symbolic, ethical, and cosmological weight. They feature prominently in riddles (àlọ́ àpamọ̀), incantations (ọfọ̀), and proverbs (òwe) [S5, S8]. The three examples below illustrate how traditional numeral words function in cultural discourse:
Ẹ̀rìnlélógún kì í ṣe eéjìdínlọ́gbọ̀n, bẹ́ẹ̀ ni ogún kì í ṣe ọgbọ̀n.
Four-added-to-twenty not be two-subtracted-from-thirty, thus is twenty not be thirty.
Twenty-four is not twenty-eight, just as twenty can never be thirty. (translated by author, confidence: medium)
This proverb directly pairs the additive formation ẹ̀rìnlélógún (20 + 4 = 24) with the subtractive formation eéjìdínlọ́gbọ̀n (30 - 2 = 28). In Yorùbá rhetoric, it is used to rebuff attempts to conflate two distinct social realities or to assert that boundaries, ranks, and categories must remain distinct. Stripping tone marks collapses ogún (twenty, M-H) with ògùn (medicine, L-L) or Ògún (the deity of iron, L-H), destroying the mathematical meaning.
Ọgọ́rùn-ún owó kì í kárí àpò, ẹgbẹ̀wá owó kì í kárí àwùjọ.
Five-twenties money not be-enough bag, ten-two-hundreds money not be-enough assembly.
A hundred cowries cannot fill a money-bag, two thousand cowries cannot suffice for a gathered multitude. (translated by author, confidence: medium)
The saying contrasts ọgọ́rùn-ún (100 cowries) with ẹgbẹ̀wá (2,000 cowries, which formed one standard head of currency, ọwọ́ kan). It is deployed in communal deliberations to emphasize that substantial communal projects require substantial resources rather than token contributions.
Ẹẹ́rìndínlógún lẹnu Ifá, oókan dín níbẹ̀ kò ṣe é dá.
Four-subtracted-from-twenty is-mouth Ifá, one subtracted from-there not do to cast.
Sixteen is the mouth of Ifá, if one is missing, divination cannot be cast. (translated by author, confidence: medium)
This liturgical verse cites the sixteen principal Odù of Ifá using the classical subtractive term ẹẹ́rìndínlógún (20 - 4 = 16). It asserts the completeness and inviolability of the esoteric corpus, warning initiates that ritual protocols cannot be performed with partial knowledge.
While secular counting in southwestern Nigeria has shifted toward English, the traditional vigesimal numeral vocabulary remains preserved across the Afro-Atlantic diaspora, particularly in Cuban Lucumí (Santería / Regla de Ocha) and Brazilian Candomblé Ketu [S13, S16].
In Cuban Lucumí, diviners cast sixteen consecrated cowrie shells in a system known as el Diloggún (derived from Yorùbá ẹẹ́rìndínlógún) [S13, S16]. The signs (odun) are identified and ranked by the number of cowrie shells that land with their open aperture facing upward [S13, S16]. The Lucumí names for these numerical casts preserve nineteenth-century Yorùbá number words and Odù names in Spanish orthography:
+-------+-------------------------+---------------------------+----------------------------------------------+
| Value | Standard Yorùbá Root | Lucumí Diloggún Name | Liturgical Association in Diaspora [S13, S16] |
+-------+-------------------------+---------------------------+----------------------------------------------+
| 1 | Ọ̀kan / Ọ̀kànràn | Okana | Elegguá; difficult path, solitary beginning |
| 2 | Èjì / Èjìokò | Ejioko | The Ibeyi / Ochosi; double blessings |
| 3 | Ẹ̀ta / Ògúndá | Ogundá | Oggún; struggle, cutting, iron |
| 4 | Ẹ̀rin / Ìròsùn | Iroso | Changó / Yemayá; fire, deep vision |
| 5 | Àrún / Ọ̀ṣẹ́ | Oche | Ochún; fertility, beauty, sweetness |
| 6 | Ẹ̀fà / Ọ̀bàrà | Obara | Changó; prosperity from humility |
| 7 | Èje / Òdí | Odi | Yemayá; secrets, ocean, reproduction |
| 8 | Ẹ̀jọ / Èjìogbè (Ẹyẹlẹ) | Eyeunle (Unle) | Obatalá; purity, highest blessing, light |
| 9 | Ẹ̀sán / Ọ̀sá | Osa | Oyá; winds, ancestors, transformation |
| 10 | Ẹ̀wá / Òfún | Ofun | Obatalá; mystery, hidden dangers, white cloth |
| 11 | Ọ̀kanlá / Ọ̀wọ́nrín | Ojuani | Babalú-Ayé; adversity, spiritual tests |
| 12 | Èjìlá / Èjìláṣẹbọra | Ejila Shebora | Changó; ultimate triumph, royal power |
| 13 | Ẹ̀tàlá / Ìká | Metanlá | Babalú-Ayé; illness, patient endurance |
| 14 | Ẹ̀rìnlá / Òtúrúpọ̀n | Merinlá | Nana Burukú; ancestral wisdom |
| 15 | Ẹ́ẹ́dógún / Òfúnkànràn | Marunlá | Obatalá / Oshún; sudden elevation |
| 16 | Ẹẹ́rìndínlógún / Ìrẹtẹ̀ | Meridilogún | Highest assembly of Orisha |
+-------+-------------------------+---------------------------+----------------------------------------------+
Sources: Bascom (1980: 12-28) ; Cabrera (1980: 54-68) .
Notice that for numbers 13, 14, 15, and 16, Lucumí retains the additive teens mẹ́tàlá (Metanlá) and mẹ́rìnlá (Merinlá), as well as a phonetic blend Marunlá (for 15) and Meridilogún (for 16) [S13, S16]. The preservation of these number words across two centuries of linguistic isolation in Cuba demonstrates that religious liturgy functions as an effective preservative for archaic numeral systems.
In Bahia, Brazil, Candomblé Ketu temples utilize the jogo de búzios (sixteen cowries) to divine the will of the orixás . Brazilian ialorixás and babalorixás count the cast shells using Ketu-Yorùbá numeral chants (okan, meji, meta, merin, marun, mefa, meje, mejo, mesan, mewa) during the festa de orixá and ritual offerings [S13, S16].
In natural language processing (NLP) and software engineering, the complex derivational morphology of Yorùbá numerals has made them a productive subject for computational modeling and algorithmic translation .
Because Yorùbá numerals follow a rigorous recursive arithmetic logic despite their morphological irregularities, computer scientists have successfully modeled the entire system using formal grammars .
In 2014, Olúgbénga O. Akinadé and Ọdẹ́túnjí A. Ọdẹ́jọbí published a landmark computational study titled "Computational modelling of Yorùbá numerals in a number-to-text conversion system" in the Journal of Language Modelling . The authors developed a Context-Free Grammar (CFG) and finite-state automata capable of translating any Arabic numeral between 1 and 40,000,000 into its grammatically and tonally correct standard Yorùbá text equivalent .
The Akinadé-Ọdẹ́jọbí system formalizes four distinct morphophonological modules :
The system achieved 100% recall against a gold-standard corpus of attested Yorùbá numerals, demonstrating that the traditional numeral system, despite its apparent complexity, is fully computable and algorithmically regular .
+----------------------------+
| Input: Integer (e.g. 74) |
+----------------------------+
|
v
+----------------------------+
| Arithmetic Decomposition |
| (80 - 10) + 4 |
| Base: ogún (20) |
+----------------------------+
|
v
+----------------------------+
| Lexical Mapping |
| 4 -> ẹrin |
| + -> lé |
| 70 -> àádọ́rin (80 - 10) |
+----------------------------+
|
v
+----------------------------+
| Morphophonological Rules |
| ẹrin + lé + àádọ́rin |
| Vowel coalescence & tone |
+----------------------------+
|
v
+----------------------------+
| Output: ẹ́ẹ̀rìnléláàdọ́rin |
+----------------------------+
Contemporary Yorùbá language revitalization efforts increasingly rely on mobile phone applications, web dictionaries, and interactive video channels [S14, S15]. Apps such as Yorùbá101, Ọ̀nkà Yorùbá, and digital dictionaries produced by native-speaker computational linguists teach children traditional counting through gamified interfaces .
These digital platforms frequently provide parallel modes:
By presenting both systems side by side, modern software tools allow contemporary learners to navigate between cultural heritage and modern computational utility.
Scholarship on the Yorùbá numeral system across the past two centuries converges on several key points while leaving specific questions open for ongoing research:
An analysis of the Yorùbá three-level register tone system, demonstrating through minimal pairs and grammatical operations why tone is an essential phonemic component rather than optional decoration.
The Yorùbá sound system and its three tones, with worked minimal pairs showing how pitch alone changes a word's meaning.
What oríkì are, the different kinds, who performs them and why, and how they carry history that written records do not.
An investigation into how the Yorùbá numeral system quantifies load weight, agricultural land, market cycles, calendar spans, and modern temporal reckoning.
A structural and linguistic analysis of the Yorùbá vigesimal numeral architecture, examining basic roots, anchor numbers, cyclic operations, and theoretical debates.
An analytical examination of the subtractive morpheme dín and its derivational role in the Yorùbá vigesimal numeral system from 15 to 199.