Compound adjectives are made up of a combination of noun plus adjective, noun plus participle, or adjective plus participle. More often than not, these are hyphenated.
Let’s look at a few.
If you know a boy who is prone to accidents, he’s an:
Accident-prone boy
You admire a girl’s dress that is the blue of a cornflower:
Cornflower-blue dress
You’ve given your child too many lollies; she’s a:
Sugar-happy toddler
If you use a computer to create your logo, you have a:
Computer-generated logo
If you have a carpenter build cabinets to your specifications, you have:
Custom-built cabinets
You have a beautiful piece of pottery that was fired in a kiln:
Kiln-fired pottery
If you quickly thought of an answer to a dilemma, you are a:
Quick-thinking individual
If you meet a tall, dark, handsome stranger on the train, he’s a:
Good-looking man
If you were flummoxed by the good-looking man, you were:
Open-mouthed staring
Phrasal verbs are made up of a main verb and a preposition or an adverb:
Build up: You should build up the front of this flower bed.
Break in: She wants to break in her new shoes before the dance.
Drop off: He will drop off the check tomorrow afternoon.
When these phrasal verbs are used as a noun, however, you hyphenate them.
Build-up: The soap scum build-up is hard to remove from the shower.
Break-in: The neighbors next door suffered a break-in last night.
Drop-off: The drop-off at the edge of the road was terrifying.
Only when these compound adjectives precede a noun do we hyphenate them. When they fall after the noun they modify, there’s no hyphenation.
The party put forth a well-intentioned plan for rehabilitating the neighborhood.
The party’s plans for rehabilitation were well intentioned.
That boy has an interesting conch-shaped ear.
That boy’s ear is interestingly conch shaped.
The school has a government-mandated lunch program.
Clear? No?
Check out our full dashes vs hyphens article here.