What is a compound word?
A compound word is made by joining two or more smaller words to make a new word with its own meaning.
- sun + flower = sunflower
- rain + bow = rainbow
- foot + ball = football
- tooth + brush = toothbrush
Each smaller part is a base word, a word that can stand on its own. Compound words are a great way for young readers to tackle long words: if you can read the two short words, you can read the long one.
How the meaning works
Often the meaning is easy to guess from the parts:
- A bookshelf is a shelf for books.
- A snowman is a man made of snow.
- A doghouse is a house for a dog.
Usually, the second word tells you what kind of thing it is, and the first word describes it. A houseboat is a boat you live in; a boathouse is a house for boats.
Sometimes the meaning is a surprise:
- A butterfly is not a fly made of butter.
- A hotdog is not a warm dog.
- A pineapple is not an apple from a pine tree.
These are fun to talk about, and they show that language does not always follow logic.
Three kinds of compound words
Closed compounds
A closed compound is written as one word: notebook, bedroom, playground, cupcake, firefighter, grandmother.
Open compounds
An open compound has a space between the words, but the words still work together as one idea: ice cream, school bus, high school, living room, post office.
Hyphenated compounds
A hyphenated compound uses a hyphen to join the words: mother-in-law, well-known, part-time, ten-year-old, self-esteem.
| Closed | Open | Hyphenated |
|---|---|---|
| sunlight | full moon | sun-dried |
| bathroom | dining room | up-to-date |
| baseball | ice hockey | warm-up |
How do you know which kind to use? There is no single rule, and some compounds change over time (e-mail became email). When in doubt, check a dictionary.
Hyphens before nouns
Many describing phrases are hyphenated when they come before a noun but not after it.
- a well-known author but the author is well known
- a ten-year-old girl but the girl is ten years old
Reading strategy for long words
When you see a long word, look for two smaller words inside it.
- Cover the second half with your finger: rattle | snake.
- Read the first word: rattle.
- Read the second word: snake.
- Put them together: rattlesnake.
Compound words in spelling
When you join two words, keep all the letters of both, even if the same letter appears twice: book + keeper = bookkeeper, room + mate = roommate, with + hold = withhold.
Plurals of compound words
- Closed compounds add -s at the end: toothbrushes, cupcakes.
- Open and hyphenated compounds usually make the main word plural: mothers-in-law, passers-by, bus stops.
Worked examples
Example 1: Split the compound. earthquake → earth + quake.
Example 2: Make compounds with sun. → sunshine, sunset, sunburn, sunglasses.
Example 3: Closed, open or hyphenated? living room → Open.
Common mistakes
- Dropping a letter: bokeeper ✗ → bookkeeper ✓
- Writing a lot as one word: alot ✗ → a lot ✓ (it is not a compound)
- Mixing up everyday (adjective: everyday clothes) and every day (I read every day).
Try it yourself
- Make compound words: snow + flake, cow + boy, sea + shell.
- Split: grasshopper, backpack, lighthouse.
- Find the compound word: We ate popcorn in the backyard.
- Which is correct: a two-hour movie or a two hour movie?
Answers: 1. snowflake, cowboy, seashell. 2. grass+hopper, back+pack, light+house. 3. popcorn, backyard. 4. a two-hour movie.
Tip for families
Make compound word puzzles. Write each half of a compound on a separate card (rain / coat, star / fish) and mix them up. Match the pieces, then invent silly new compounds (fishcoat?) and draw what they would look like.
Quick recap
- Compound words join two or more words into one new word.
- They can be closed, open or hyphenated.
- The second word usually names the thing; the first describes it.
- Look for small words inside long ones to help you read.