... #1.Plural Rule #1: Add -s or–es Add -s-s to most words to make them plural. If a word ends in -s-s, -x-x, -z-z, -sh-sh, or -ch-ch, add -es-es. 6493_LE _Spelling( FIN).indd 1266493_LE _Spelling( FIN).indd ... road, butter, theory-s, -es, -er, -ness, -age, -ant, -entverb names an action run, play, fl oat-s, -es, -ing, -ed, -ify, -en6493_LE _Spelling( FIN).indd 1106493_LE _Spelling( FIN).indd 110 ... change the -um or -on to an -a when forming plurals. Some words that end in -us change the -us to an -i. Some words that end in -is change the -is to an -es. Some words that end in -ex or -ix change...