A part of speech is a term used in traditional grammar for one of the nine main categories into which words are classified according to their functions in sentences, such as nouns or verbs. Also known as word classes, these are the building blocks of grammar. Parts of Speech Word types can be divided into nine parts of speech: nouns pronouns verbs adjectives adverbs prepositions conjunctions articles/determiners interjections Some words can be considered more than one part of speech, depending on context and usage. Interjections can form complete sentences on their own.