What is the plural of the word 'child'?

The plural of “child” is “children.” It is an irregular plural, so it does not follow the usual English pattern of adding -s or -es. The form developed from Old English, in which the singular was “cild” and an older plural form was “cildru.” Over time, Middle English forms such as “childre” combined with the plural ending -en, producing “children.”

The word therefore preserves more than one layer of historical change: the ending reflects an older plural pattern, while the spelling and pronunciation evolved through later stages of English. Similar -en plurals survive in a few other words, most notably “oxen,” although they are uncommon in modern English.

“Childrens” is not the standard plural. The form “children’s” is correct when showing possession, as in “the children’s books,” but the apostrophe and possessive ending do not make it an ordinary plural. “Childs” can appear in rare names or specialized compounds, but it is not the normal plural in standard English. The same word can also be used attributively without changing form, as in “child psychology.”