What’s the difference between state-of-the-art technology and technology being state of the art? Compound modifiers are two or more words expressing a single concept, as in the previous example. Hyphenating in this context is very commonly done the wrong way. So we’re here to clear things up.

Depending on where in a sentence you use compound modifiers decides whether or not you hyphenate them.

Most simply, these words are hyphenated when they are used before a noun to be used as an adjective:

We had an action-packed weekend.

In this case, weekend (the noun) is being described by action-packed (the adjective). Therefore, a hyphen is used.

They aren’t hyphenated when they come after the noun:

Our weekend was action packed.

As with any rule in the English language, there are (of course) exceptions. Compound modifiers are not hyphenated before the noun if the word very or an adverb ending in –ly is used:

The very hot sun burned our skin. VS. The white-hot sun burned our skin.

Here are a few more comparative examples to illustrate how it works:

She ran her fingers through his salt-and-pepper hair.

His hair was salt and pepper in colour.

He quit his part-time job.

His job was part time, so he quit.

She is a well-known seamstress in her community.

That seamstress is well known in her community.

He stepped outside to feel the bone-chilling cold on his face.

The cold he felt on his face was bone chilling.