The parts of speech are a system for classifying words.

There are eight parts of speech: noun, pronoun, verb, adjective, preposition, conjunction and interjection.

Many words can function as more than one part of speech.

For example, depending on its use in a sentence,

the word paint can be a noun (the paint is wet) or a verb (Please paint the ceiling next).

Further nouns, are classified for a variety of purposes

When capitalization is the issue, we speak of proper versus common nouns