What Are Compound Words: Understanding Dual-Word Constructions

Three Types of Compound Words — See the Pattern

Look at these words. Can you see how they are different?

• notebook — one word, no space (note + book)
• ice cream — two words, with a space (ice + cream)
• mother-in-law — words joined by a dash (mother + in + law)

Did you see the pattern? All three are compound words. But they are written in different ways. English has three types of compound words:

How to Know Which Type a Compound Word Is

This is the hard part. There is no simple rule that tells you when to use a space, when to join the words, and when to use a dash. You often just need to learn each word. But here are some helpful patterns:

Closed compounds — words that people use together very often become one word over time.

• bedroom (bed + room)
• toothpaste (tooth + paste)
• homework (home + work)

Open compounds — the two words stay apart, but they mean one thing together.

• living room (a room for living in)
• high school (a type of school)
• post office (a place for sending mail)

Hyphenated compounds — the dash helps make the meaning clear. Many describing words before a noun use a dash.

• a well-known singer (well + known)
• my mother-in-law (mother + in + law)
• a long-term plan (long + term)

Easy way to remember: If you are not sure, check a dictionary. Over time, many open compounds become closed. For example, “e mail” became “e-mail” and then “email.”

Compound Words You Already Know

You probably use compound words every day without thinking about it. Here are some you know:

• I need to buy some toothpaste. (closed — tooth + paste)
• She forgot her password again. (closed — pass + word)
• Let’s get some ice cream after lunch. (open — ice + cream)
• My daughter starts high school next year. (open — high + school)
• He is a well-known actor in my country. (hyphenated — well + known)

You are doing great. Now let’s look at the mistakes many learners make.

Three Mistakes to Avoid With Compound Words

Even native speakers get compound words wrong sometimes. The spelling changes depending on which dictionary you use, and some words have changed over the years. So if you get confused, you are not alone.

How to remember: When you learn a new compound word, write down which type it is — closed, open, or hyphenated. Over time, you will remember the common ones without thinking.

Here are more common compound words to practise with:

Test Yourself: Closed, Open, or Hyphenated?

Choose the correct answer for each sentence. Click Check to see if you are right.

Keep Going — You Are Building Something

You just learned the three types of compound words. That is one more grammar topic you will never get confused by again.

But here is something interesting. You know that “ice cream” is two separate words. But what about apart and a part? They look almost the same, but they mean completely different things. Do you know which one to use when you say “I want to be _______ of this team”?

Next lesson: A Part vs Apart — What’s the Difference?