Nouns are naming words that can refer to people, places, objects, ideas, emotions, qualities and activities. There are two main types of nouns: proper nouns and common nouns. Common nouns can be further divided into countable nouns, uncountable nouns, concrete nouns and abstract nouns. Countable nouns can be pluralized and take determiners like "a" or "an", while uncountable nouns cannot be pluralized or take determiners. Concrete nouns refer to tangible things while abstract nouns refer to intangible concepts. Noun phrases consist of a noun and accompanying words that function as the subject or object of a clause.