Getting Nigerian English Instead of Generic English From AI

Nigeria has one of the largest English-speaking populations of any country — the UN’s World Population Prospects puts the national population above two hundred million, and English is the official language. A model asked for “English” nonetheless writes American English, and asked for “Nigerian English” often writes Pidgin instead. Both are fixable, but only if you say which one you want.

Decide which variety you mean

Three distinct things share the label, and conflating them is the single most common reason the output comes back wrong.

• Nigerian Standard English — the formal written variety of newspapers, government, banking and business correspondence. Fully standard English, with its own lexis, its own preferred register, and British-derived spelling.
• Nigerian English in informal use — the same variety in conversational register, where the distinctive vocabulary and idiom are most visible.
• Nigerian Pidgin (Naijá) — a separate English-lexifier creole with its own ISO 639-3 code, pcm. It has its own grammar: dey as a progressive marker, don as a perfective, na as a copula and focus marker, go as a future. “I dey come” is not badly spelled English; it is correct Pidgin. The BBC has published a full news service in it since 2017, which is one of the largest edited corpora of the language.
• Nigeria’s major indigenous languages — Yoruba, Igbo, Hausa — are separate languages again, covered in how well models support Yoruba. Asking for “Nigerian” without qualification is ambiguous across all of these.

If you are writing customer communications for a Nigerian bank, you want the first. If you are writing social copy for a young audience, you may want the second or a measured amount of the third. Saying so in the prompt is not pedantry; it is the whole instruction.

Lexis a generic prompt flattens away

Nigerian English is codified enough to be documented in general reference works. In its January 2020 update, the Oxford English Dictionary added a set of Nigerian English entries and senses — among them danfo, okada, tokunbo, buka, mama put, barbing salon, next tomorrow, send-forth, K-leg, gist, guber, non-indigene, ember months, and Nigerian senses of chop, severally and put to bed. That update is a useful anchor precisely because it is a citable, dated, third-party record rather than a list somebody assembled.

Nigerian English        gloss
next tomorrow           the day after tomorrow
severally               on several occasions
gist                    chat, gossip (noun and verb)
flash me                ring and hang up, so I have your number
I'm coming              I'll be back shortly
well done               greeting to someone who is working
how far?                informal greeting
on / off the light      switch the light on / off (verbs)
escort me               walk part of the way with me
dash                    give as a gift; a gift
wash                    a celebration marking a purchase
tokunbo                 second-hand, imported
danfo / keke / okada    minibus / tricycle taxi / motorcycle taxi
ember months            September to December
do the needful          do what is required
revert                  reply
kindly                  please (standard in formal register)

A few grammatical patterns travel with the lexis: stative verbs in the progressive (I am having a car, I am hearing you), mass nouns pluralised (equipments, informations), and isn’t it? as an invariant tag. Whether you want those depends on the register — they are ordinary in speech and edited out of a bank’s formal correspondence — which is exactly why you must set register separately from variety.

Formal register is the harder half

The distinctive thing about Nigerian formal English is not vocabulary at all. It is a markedly more elaborate, more courteous register than contemporary American business writing, with formulae that a model trained mostly on American corporate prose will silently strip out: opening with a reference to previous correspondence, addressing readers as Sir or Ma, professional title prefixes used before names (Engr., Barr., Arc., Pharm., Chief, Alhaji), and closing formulae that are fuller than a bare “Thanks”.

A model told only “write in Nigerian English” will typically keep American brevity and add slang — producing something that reads as a foreigner imitating Nigerian speech, which is worse than plain American English for a professional audience. The register instruction is the one that does most of the work, and it is a separate instruction from the variety.

Spelling, dates, money

• Spelling follows British convention. colour, organise, centre, programme, cheque, enrolment. American spelling is the loudest tell that a text was generated with no locale set — see British and American spelling in AI output.
• Dates are day-first. 14 August 2026 or 14/08/2026. A generated 08/14/2026 is wrong and, worse, ambiguous.
• Currency is the naira, symbol before the amount — ₦250,000 — with the ISO code NGN where a symbol will not render. Comma thousands separator, full-stop decimal.
• Phone numbers. International form is +234 followed by the number with its leading zero dropped.
• Time zone is WAT, UTC+1, with no daylight saving. Anything that computes a local time and applies a summer offset is wrong all year.

Building the prompt

1. State the variety and the register in one sentence: “Write in Nigerian Standard English, formal business register, for a Lagos professional audience. Do not use Nigerian Pidgin.” The negative clause matters — without it, “Nigerian” pulls toward Pidgin.
2. Add the conventions as hard constraints: British spelling, day-first dates, naira with the symbol before the figure, WAT for times.
3. Supply a short lexis list of the terms that belong in this document and a deny-list of the ones that do not. For a formal letter the deny list is the informal column above.
4. Give one demonstration — a real paragraph in the target register — rather than more adjectives. Put it before anything that varies per request so it sits in a cacheable prefix.
5. Send it, and validate mechanically before a human reads it.

POST /v1/chat/completions
{
  "model": "<your-model>",
  "temperature": 0.4,
  "messages": [
    {
      "role": "system",
      "content": [
        "Write in Nigerian Standard English, formal business register,",
        "for a Nigerian professional audience.",
        "Do NOT use Nigerian Pidgin.",
        "Conventions: British spelling (colour, organise, cheque);",
        "dates as 14 August 2026; currency as NGN with the naira symbol",
        "before the amount; times in WAT (UTC+1, no daylight saving).",
        "Address the reader as Sir or Ma where a salutation is needed and",
        "keep professional title prefixes (Engr., Barr., Arc., Chief) intact.",
        "Avoid American idiom and avoid slang."
      ].join(" ")
    },
    {
      "role": "user",
      "content": "Draft a letter to a customer confirming that their loan restructuring request of 3 August has been approved, stating the new monthly repayment of NGN 148,500 from September."
    }
  ]
}

Checking the output

Three of the four checks are automatable, and automating them is what keeps this reliable across a whole batch rather than on the one example you looked at.

• Spelling. Regex for -ize, color, center, check in the banking sense. Any hit is a defect.
• Format. Regex for \d{1,2}/\d{1,2}/\d{4} and reject month-first; confirm the currency symbol or NGN precedes the figure.
• Pidgin leakage. Match on \b(dey|na|abeg|wetin|don)\b for documents that must be Standard English. These are Pidgin function words and have no place in a formal letter.
• Register. Not automatable. Have a Nigerian reader check one document per template, once. What they will catch is tone — a letter that is correct in every mechanical respect and reads as curt.