Count nouns can be counted and have both a singular and plural form. A or an is used with singular count nouns when they are indefinite or general. Examples given are "a book" and "an apple". Non-count nouns cannot be counted and only have one form without a plural. Quantifiers like "a bottle of milk" or "bottles of milk" are used with non-count nouns instead of a/an. Common non-count nouns provided are milk, money, happiness.