I. noun plural suffix
Etymology: Middle English -es, -s, from Old English -as, nominative & accusative plural ending of some masculine nouns; akin to Old Saxon -os
— used to form the plural of most nouns that do not end in s, z, sh, ch, or postconsonantal y <heads> <books> <boys> <beliefs>, to form the plural of proper nouns that end in postconsonantal y <Marys>, and with or without a preceding apostrophe to form the plural of abbreviations, numbers, letters, and symbols used as nouns <MCs> <PhD's> <4s> <the 1940's> <$s> <B's> — compare -es I II. adverb suffix Etymology: Middle English -es, -s, plural ending of nouns, from -es, genitive singular ending of nouns (functioning adverbially), from Old English -es — used to form adverbs denoting usual or repeated action or state <always at home Sundays> <mornings he stops by the newsstand> III. verb suffix Etymology: Middle English (Northern & North Midland dialect) -es, from Old English (Northumbrian dialect) -es, -as, probably from Old English -es, -as, 2d singular present indicative ending — more at -est — used to form the third person singular present of most verbs that do not end in s, z, sh, ch, or postconsonantal y <falls> <takes> <plays> — compare -es II
New Collegiate Dictionary. 2001.