The combining form -ful is used to form nouns meaning ‘the amount needed to fill’ ( cupful , spoonful , etc.). The plural form of such words is cupfuls , spoonfuls , etc. Three cups full would denote the individual cups rather than a quantity measured in cups: on the sill were three cups full of milk ; add three cupfuls of milk to the batter .
More definitions of -fulDefinition of -ful in:
- The British & World English dictionary