A part of speech is a category of words which have similar grammatical properties. Words that are assigned to the same part of speech generally display similarly—they play similar roles within the grammatical structure of sentences. Commonly listed English parts of speech are noun, verb, adjective, adverb, pronoun, preposition, conjunction, interjection (08 parts of speech).
Many English words can belong to more than one part of speech. Words like neigh, break, outlaw, laser, microwave, and telephone might all be either verbs or nouns.