Ordinal Suffix

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Functions

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addOrdinalSuffix(number)

addOrdinalSuffix(number?: string): string

import { addOrdinalSuffix } from "@persian-tools/persian-tools";

addOrdinalSuffix("سه"); // "سوم"
addOrdinalSuffix("دو"); // "دوم"
addOrdinalSuffix("پنج"); // "پنجم"
addOrdinalSuffix("سی و سه"); // "سی و سوم"
addOrdinalSuffix("یکصد"); // "یکصدم"

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Rules (applied in order)

1. Ends with ی → append اُم (leading space + standalone اُم).
2. Ends with سه → strip last 2 chars, append سوم.
3. Otherwise → append م.

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Input

• Must be a string. Anything else throws TypeError("PersianTools: addOrdinalSuffix - The input must be string").
• "" does NOT throw — it falls through rule 3 and returns "م". Validate non-emptiness upstream if needed.

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removeOrdinalSuffix(word)

removeOrdinalSuffix(word: string): string

import { removeOrdinalSuffix } from "@persian-tools/persian-tools";

removeOrdinalSuffix("سوم"); // "سه"
removeOrdinalSuffix("یازدهم"); // "یازده"
removeOrdinalSuffix("بیستم"); // "بیست"
removeOrdinalSuffix("سیزدهمین"); // "سیزده"
removeOrdinalSuffix("سه هزارم"); // "سه هزار"
removeOrdinalSuffix("چهاردهمین"); // "چهارده"

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Behaviour

1. Falsy input is returned as-is (no throw, no "" coercion).
2. Generic suffixes are removed: مین, ام, اُم.
3. A table of irregular forms is applied (longest matches first) — e.g. سوم → سه, یازدهم → یازده, دوازدهم → دوازده.

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Pitfalls

• addOrdinalSuffix("") returns "م" (a single character), not "". Validate upstream.
• addOrdinalSuffix(null) throws TypeError, doesn’t return "".
• removeOrdinalSuffix(null) returns null unchanged (falsy input passes through).
• اول is not handled by removeOrdinalSuffix — it returns "اول" unchanged (no built-in mapping to یک).
• Rule coverage is conservative. addOrdinalSuffix("یک") returns "یک اُم" (rule 1: ends with ی), which is grammatical but uncommon; the colloquial "یکم" is not produced. Confirm against your style guide.

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Composition with Number to Words

import { numberToWords } from "@persian-tools/persian-tools";

numberToWords(5, { ordinal: true }); // "پنجم"
// equivalent to addOrdinalSuffix(numberToWords(5))

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Source