Pluralize English words without the classic bugs

'1 item' / '3 items' is easy until the word is 'memory' or 'criterion'. Rule-based pluralization that knows its exceptions.

Tools used in this guide

The job

UI strings, generated messages, test fixtures — anywhere code writes English, the naive '+s' produces 'boxs' and 'childs'. Real rules cover -y, -s/-x/-ch endings, -f/-fe words, and the irregulars (child→children, criterion→criteria, person→people) that rules alone get wrong.

One word or a column

Single word gives the plural; paste a whole list (one per line or comma-separated) and get every plural back. Caps are preserved — CHILD → CHILDREN — and a singularize direction reverses it for checking existing text.

Uncountable words (sheep, information, furniture) return unchanged — no 'informations'.
Tricky '-fe' words resolve by dictionary, not by a blanket rule — 'safe' becomes 'safes', while 'knife' becomes 'knives'.

Where it ends

English only, count-forms only — 'two pieces of news' phrasing is a copywriting problem, not a morphology one. Input limit 100,000 words.