THE SPELLING OF NOUNS IN THE PLURAL
Changes from the singular to the plural in a proof negligently revised sometimes put upon a compositor the duty of making a proper plural. It is usually formed by adding s to the word in the singular number, as bamboo, bamboos; cameo, cameos; folio, folios; octavo, octavos. When the added s makes another syllable (as it does in hiss, hisses; sash, sashes), and sometimes when it does not (as in buffalo, buffaloes; potato, potatoes; negro, negroes; hero, heroes), es is added.
When the noun ends in y, preceded by a consonant, the y is changed in the plural to ies, as in dainty, dainties; pygmy, pygmies; spy, spies.
Some words ending in f or fe change the f for v in the plural, as half, halves; shelf, shelves; knife, knives. Fifes, proofs, and strifes are exceptions. Nouns in common use, derived from foreign languages, usually form their plurals according to the general English rule, as index, indexes; cherub, cherubs; formula, formulas; seraph, seraphs; beau, beaus; but in scientific writings the plurals should be formed according to the rules of the language from which the words have been derived, as in
- appendix, appendices
- beau, beaux
- medium, media
- formula, formulae
- index, indices
- cherub, cherubim
- seraph, seraphim
- vortex, vortices
