Guide to Grammar and Usage Singular city lady Plural cities ladies 293 · If the noun ends in y preceded by a vowel, add s. Singular essay monkey Plural essays monkeys · If the noun ends on o preceded by a vowel, add s. Singular radio ratio Plural radios ratios · If the noun ends in o preceded by a consonant, the noun can takes es, s, or either s or es. Singular Takes es potato hero Takes s silo solo Either zero tornado zeros, zeroes tornados, tornadoes silos solos potatoes heroes Plural · Add s to most nouns ending in f. Singular brief chief Plural briefs chiefs Exceptions:Change the f or fe to v and add es. Singular self wolf leaf knife life wife half thief Plural selves wolves leaves knives lives wives halves thieves · In compound words, make the main word plural. Singular sister-in-law mother-in-law Plural sisters-in-law mothers-in-law · Some nouns change their spelling when they become plural.