Plural Singular Converter

English pluralisation is regular often enough to automate and irregular often enough to need checking. The productive rules cover most cases: add -s, add -es after s, x, z, ch, and sh, change -y to -ies after a consonant, and change -f or -fe to -ves for a subset of words. Applied blindly, those rules produce childs, mouses, and analysises, so the exceptions have to be handled by lookup rather than by pattern.

The awkward categories are worth knowing before trusting any converter. Latin and Greek borrowings keep their original plurals in formal registers — criterion becomes criteria, phenomenon becomes phenomena, index becomes either indices or indexes depending on field. Several nouns are invariant, so sheep, series, and species look identical in both numbers. And uncountable nouns like software, information, and equipment have no plural at all, though converters will happily invent one.

The real-world reason this matters is interface copy. "1 items found" is the classic symptom of a template that never handled the singular case, and it reads as careless in a way users notice immediately. Handle the count of one explicitly rather than appending an s conditionally, and remember that other languages have more than two number forms — Polish and Russian have several — so a design that assumes singular-or-plural will not survive localisation.