Parts of Speech (often abbreviated to PoS and sometimes known as Word Classes) are the different categories of words‎ in English. They refer to the way in which those words are used grammatically.

For example, if you look at the following sentences‏‎ you can see that although the words in bold are all different, they all work the same way in the sentence.

Have you seen that old man?
Have you seen that attractive man?
Have you seen that poor man?

Obviously the words old, attractive and poor are grammatically related in some way and can be put into the same category. In this case they are all words which describe; in English these are known as adjectives.

The Different Parts of Speech

In the example above it’s fairly easy to classify identify those words which fit in the category of adjective.

However, it isn’t always so easy with other classes and grammarians have classed words differently throughout history. This means that there is no single set of parts of speech, or word classes, that everyone agrees on. However, this is a reasonable start:

• Adjectives‏‎ – words which describe objects & things, e.g. red, old, big…
• Adverbs ‏‎– words which say how something is done, e.g. quickly, happily, foolishly…
• Conjunctions ‏‎– words which join parts of sentences together, e.g. and, but, also…
• Determiners‏‎ – words which say how many, e.g. some, all, these, those… (including the Articles‏‎ a, an, the)
• Nouns – objects or things, e.g. ball, dog, love… (including Pronouns‏‎ e.g. I, you, he, she)
• Prepositions -‏‎ which tell us when or where and when, e.g. under, over, at, after…
• Verbs – words which describe actions, e.g. run, walk, read…

But don’t forget that since not everyone agrees on what word classes there are you may well see other categories elsewhere!

If you look up a word in a good dictionary you’ll often see not only an explanation of the meaning of the word, but also the grammatical class which it belongs to.

banana noun (bananas) 1 a large perennial SE Asian plant, superficially resembling a tree, that is cultivated throughout the tropics as a staple food crop. 2 the long curved fruit of this plant, which is often sold as an unblemished yellow fruit, but which is not fully ripe until it is flecked with brown spots. be or go bananas slang to be or become crazy.
ETYMOLOGY: 16c: from the native name in Guinea. *

* definition from Chambers Dictionary.

However, remember that some words can belong to more than one class or part of speech. In this case the word fleece is a noun or a verb.

fleece noun 1 a sheep’s woolly coat. 2 a sheep’s wool cut from it at one shearing. 3 sheepskin or a fluffy fabric for lining garments, etc. 4 a garment made of fluffy acrylic thermal fabric and used like a jacket or pullover. verb (fleeced, fleecing) 1 to cut wool from (sheep); to shear (sheep). 2 slang to rob, swindle or overcharge. fleeceless adj. fleecer noun.
ETYMOLOGY: Anglo-Saxon flies.

Here the word fleece can work as a noun:

She wore a thick fleece to keep out the cold.

Or it can work as a verb:

The shopkeeper fleeced his customers until the day he was arrested.

Which Word Class?

So how do you work out what class a word belongs to?

The simple answer is to substitute it for a word which you know and see if the sentence still makes sense.

For example, this sentence contains a made-up word:

The toves played in the woods.

To work out what class toves is, we can try putting other words in its place and see what happens:

adjective: * the yellow played in the woods
verb: * the sing played in the woods
noun: the boy played in the wood
adverb: * the happily played in the wood

* an asterisk shows an ungrammatical sentence

From this we see that toves has to be a noun.

Open or Closed

Some categories are open. This means we can add new words to the category whenever the need arises. In recent years the boom in technology has meant that new devices have been created and in turn new words are needed to describe them. These words are relatively new in English and have all been added to the open class of nouns:

internet, iPod, DVD…

On the other hand, here are some pronouns‏‎ in English:

I, you, he, she, it, yours, mine…

Although there has been a slight change in the meaning of some of these, the full list has not changed in many hundreds of years and we cannot simply add a new pronoun willy nilly.