A count noun is a noun such as 'bird', 'chair', or 'year' which has a singular and a plural form and is always used after a determiner in the singular.
count noun in British English
noun
linguistics, logic
a noun that can be qualified by the indefinite article, and may be used in the plural, as telephone and thing but not airs and graces or bravery
Compare mass noun, sortal
count noun in American English
US
a noun denoting something that is countable: it can form a plural and be preceded by a or an or a numeral (Ex.: dog, tree, idea)