compound words

"Compound words" is a grammar term that describes a very common feature of English. It refers to words that are made by joining two or more separate words together to create a brand-new word with its own meaning. There are a few ways compound words can look, and this term itself is a great example — "compound" + "words" = "compound words"!

1nounclosed compound

This is when two words are joined together with no space between them, forming one single word. The new word usually has a meaning that is connected to — but different from — the two original words. Think of 'sun' + 'flower' = 'sunflower'. A sunflower is not just any flower in the sun — it is a specific type of flower!

grammar / everyday language · Modern, widely used

The word 'toothbrush' is a closed compound made from 'tooth' and 'brush'.

She wrote 'bedroom' as two separate words, but her teacher reminded her it is a closed compound.

'Notebook', 'airport', and 'football' are all examples of closed compound words.

2nounhyphenated compound

Sometimes two words are joined with a small dash (-) called a hyphen. This is very common when the compound word is used as a describing word (adjective) before a noun. For example, 'well-known' or 'up-to-date'. The hyphen shows that the two words are working together as one idea.

grammar / writing · Modern, widely used

'Self-confidence' is a hyphenated compound word you will see very often in English.

The phrase 'a well-known author' uses a hyphenated compound to describe the author.

Words like 'mother-in-law' and 'check-in' are hyphenated compound words.

3nounopen compound

Some compound words are written as two separate words with a space, but they still act as one single concept. This can be confusing because they look like two normal words sitting next to each other! For example, 'ice cream' is two words, but together they mean one specific thing — that delicious frozen dessert.

grammar / everyday language · Modern, widely used

'Ice cream', 'post office', and 'living room' are all open compound words.

Even though 'high school' is written as two words, it is treated as one compound word referring to a specific level of education.

The student was surprised to learn that 'full moon' is an open compound word.

4nounmeaning shift

One of the most interesting things about compound words is that their meaning is often different from — or more specific than — the meanings of the two words separately. You cannot always guess the meaning just by looking at the parts! For example, a 'deadline' has nothing to do with death or a line you draw — it means the last moment you have to finish something.

grammar / vocabulary learning · Modern, widely used

The compound word 'butterfly' does not literally mean a fly made of butter — it is the name of an insect.

A 'brainstorm' is not a storm inside your brain — it means to think of many ideas quickly.

Understanding meaning shifts helps you use compound words correctly instead of guessing from the parts.