Word classes

Is "running" a verb or an adjective? And how do you know if "fast" is an adverb or an adjective?

Every word in English belongs to a word class (also called a part of speech). Knowing how these classes work helps you choose the correct form and avoid common mistakes.

The main word classes

The most important word classes are:

Nouns — name people, places, things, ideas
Verbs — show actions or states
Adjectives — describe nouns
Adverbs — describe verbs, adjectives, or other adverbs
Pronouns — replace nouns
Prepositions — show relationships (in, on, under)
Conjunctions — connect ideas (and, but, because)
Determiners — limit nouns (a, the, my, some)

Nouns

A noun names something.

dog, city, table, happiness

Types of nouns:

• Common: dog, city
• Proper: London, Monday
• Abstract: love, freedom
• Concrete: apple, chair

Verbs

A verb shows action or state.

run, think, be, seem

Verbs change form depending on time (tense):

I walk → I walked → I will walk

They can also form continuous and perfect structures:

I am walking, I have walked

Adjectives

An adjective describes a noun:

a tall building, a red apple, an interesting book

They often come before the noun or after linking verbs:

The building is tall.

Adverbs

An adverb describes how, when, where, or how much.

quickly, slowly, very, here, now

Many adverbs end in -ly, but not all:

fast, hard, well

Adjective or adverb? (key distinction)

This is one of the most common mistakes.

After an action verb, use an adverb:

✔ She runs quickly.
❌ She runs quick.

After a linking verb (be, seem, look, feel), use an adjective:

✔ She looks happy.
❌ She looks happily.

Words that can belong to multiple classes

Some words change class depending on how they are used.

Running:

Running is fun. (noun)
She is running. (verb)
running water (adjective)

Fast:

a fast car (adjective)
She runs fast. (adverb)

This is why context is important — not just the word itself.

Pronouns

Pronouns replace nouns:

I, you, he, she, it, we, they

They help avoid repetition:

Maria is here. She is waiting.

How to identify the word class

Ask:

• What is the word doing in the sentence?
• Is it naming, describing, or showing action?
• What word is it connected to?

The same word can belong to different classes depending on its role.

Key idea

Word classes are not just labels — they show how words function in a sentence.

Understanding function helps you choose the correct form naturally.