The document discusses the classification of words into parts of speech according to their function in sentences. It lists the 10 parts of speech as noun, adjective, pronoun, verb, adverb, preposition, conjunction, numeral, article, and interjection. Examples are provided to illustrate the definition and use of each part of speech. The document concludes that the part of speech of a word can only be determined by seeing how it is used in a sentence.