In linguistics, measure words are words (or morphemes) that are used in combination with a numeral to indicate an amount of something represented by some noun. They denote a unit or measurement and are used with mass nouns (uncountable nouns), and in some cases also with count nouns. For instance, in English, is a mass noun and thus one cannot say *"three muds", but one can say "three drops of mud", "three pails of mud", etc. In these examples, drops and pails function as measure words. One can also say "three pails of shells"; in this case the measure word pails accompanies a count noun (shells).