Countable nouns are words that refer to items that can be counted individually. They have both singular and plural forms. For example, you can say one apple or two apples. Countable nouns can be used with numbers and can be preceded by articles like "a" or "an" in the singular form. In contrast, countable nouns can be modified by words like "many" or "few" in the plural form. Examples include books, cars, and children. These nouns help us specify quantities and are essential for clear communication in everyday language.