Word classes are parts of speech. They’re the building blocks that form every sentence ever uttered. They are categorized by the role they play in your sentences.

Everyone agrees on the following four main word classes:

1. Noun
2. Verb
3. Adjective
4. Adverb

There are varying opinions as to whether the following are word classes or word forms. So we went straight to the experts: the Oxford and Cambridge Dictionaries. Per these two highly learned sources, the following are considered word classes also:

1. Pronoun (e.g. I, you, me, we, mine, someone, he, she)
2. Preposition (e.g. at, in, on, across, behind, for)
3. Conjunction (e.g. and, but, when, if, because)
4. Determiner (e.g. a, the, an, this, etc.)
5. Exclamation or Interjection (e.g. oh, ah, wow, ouch)

The four main classes have thousands of members, and new nouns, verbs, and other words are being created every day. Consider the verb “google.” This verb didn’t exist just a few years ago and now it is firmly entrenched in everyday language. Just last month a new noun, “intersectionality” (the study of overlapping social identities and related systems of discrimination), was just added to Dictionary.com. Can you think of any other words that have recently been created and entered your own vocabulary?

Some words, however, can fall in multiple word classes depending on their context:

• Put your money in the bank. (noun)
• He began to bank the airplane into the wind. (verb)
• Come warm up by the fire. (noun)
• He will certainly fire her for coming in late again. (verb)
• A book is a source of endless reading pleasure. (noun)
• Book your holiday plans soon to get the best deal. (verb)
• She loves fast cars. (adjective)
• He’s driving fast to get to work on time. (adverb)
• Her hourly complaints have got to stop. (adjective)
• The weather report is reported hourly. (adverb)

The next step is to use your word classes to form phrase classes, like noun phrases, verb phrases, adjective phrases, etc. But we’ll save that for another post.