- aff. use a suffix meaning “full of,”“characterized by” (beautiful; careful); “tending to,”“able to” (harmful; wakeful); “as much as will fill” (spoonful)•Etymology: ME, OE -full, -ful, repr. full, ful full I usage: The plurals of nouns ending in -ful are usu. formed by adding -s to the suffix: two cupfuls. Perhaps influenced by the phrase in which a noun is followed by the adjective full (both arms full of packages), some speakers and writers pluralize such nouns by adding -s before the suffix: two cupsful.
From formal English to slang. 2014.