Traditional grammar classifies words based on eight parts of speech: the verb, the noun, the pronoun, the adjective, the adverb, the preposition, the conjunction, and the interjection.

Each part of speech explains not what the word is, but how the word is used. In fact, the same word can be a noun in one sentence and a verb or adjective in the next. The next few examples show how a word's part of speech can change from one sentence to the next, and following them is a series of sections on the individual parts of speech, followed by an exercise.

Books are made of ink, paper, and glue.

In this sentence, "books" is a noun, the subject of the sentence.

Deborah waits patiently while Bridget books the tickets.

Here "books" is a verb, and its subject is "Bridget."

We walk down the street.

In this sentence, "walk" is a verb, and its subject is the pronoun "we."

The mail carrier stood on the walk.

In this example, "walk" is a noun, which is part of a prepositional phrase describing where the mail carrier stood.

The town decided to build a new jail.

Here "jail" is a noun, which is the object of the infinitive phrase "to build."

The sheriff told us that if we did not leave town immediately he would jail us.

Here "jail" is part of the compound verb "would jail."

They heard high pitched cries in the middle of the night.

In this sentence, "cries" is a noun acting as the direct object of the verb "heard."

The baby cries all night long and all day long.

But here "cries" is a verb that describes the actions of the subject of the sentence, the baby.

The next few sections explain each of the parts of speech in detail. When you have finished, you might want to test yourself by trying the exercise.

Written by Heather MacFadyen from http://www.writingcentre.uottawa.ca/hypergrammar/partsp.html