Compound Adjectives
A well-known author, a five-year-old child, a blue-green sweater, a time-consuming task.
These descriptive phrases all employ compound adjectives—powerful tools that combine multiple words to function as a single descriptive unit.
What Are Compound Adjectives?
These multi-word modifiers function as single units to describe nouns with precision and efficiency.
Compound adjectives consist of two or more words working together to modify a noun. They appear before the noun they describe and are typically connected with hyphens to signal they function as a single modifier.
Unlike regular adjectives that stand alone (tall, blue, happy), compound adjectives create more specific, nuanced descriptions that single words cannot achieve.
Structure and Formation
Compound adjectives follow specific patterns combining different parts of speech.
These modifiers can be formed using various combinations:
- Adjective + Noun: high-quality materials, full-time job
- Noun + Adjective: sugar-free drinks, tax-exempt organization
- Noun + Noun: leather-bound book, ocean-front property
- Noun + Participle: sun-dried tomatoes, hand-made crafts
- Adverb + Participle: well-known celebrity, highly-regarded expert
- Number + Noun: two-door car, four-page document
- Adjective + Participle: new-found confidence, old-fashioned values
The Hyphenation Rule
Hyphens clarify meaning by connecting words that function as a single descriptive unit.
Key Rule
The general rule is to hyphenate compound adjectives that appear before a noun:
- She's a quick-thinking teacher.
- They live in a three-bedroom apartment.
- He gave a thought-provoking presentation.
When these same word combinations appear after the noun, hyphens typically disappear:
- The teacher is quick thinking.
- Their apartment has three bedrooms.
- His presentation was thought provoking.
Permanent Compound Adjectives
Some compound adjectives have become so established they're treated as single units.
Certain compound adjectives are so commonly used they've become permanent compounds:
- old-fashioned designs
- good-natured person
- absent-minded professor
- long-term goals
- second-hand clothes
These compounds maintain their hyphens even in dictionaries, reflecting their established status.
Number-Based Compound Adjectives
Compounds involving numbers follow specific patterns for clarity.
When numbers form part of a compound adjective, they typically require hyphens:
- twenty-five-year-old building
- two-thirds majority
- nineteenth-century literature
- five-foot-tall fence
Exception
Compounds with the word "percent" generally don't use hyphens:
- a 20 percent increase
- a 75 percent chance
Compounds with Adverbs
Adverbs ending in -ly create a special case in hyphenation rules.
The -ly Rule
Compound adjectives containing adverbs ending in -ly are generally NOT hyphenated:
- a highly regarded professor (not "highly-regarded")
- a beautifully written novel (not "beautifully-written")
- a carefully planned event (not "carefully-planned")
Other adverbs usually require hyphens:
- a well-respected community leader
- a much-admired artist
- a very-high-frequency signal
The Clarity Test
The primary purpose of hyphenating compound adjectives is to prevent ambiguity.
Consider how hyphens change meaning:
| a small-business owner | (owner of a small business) |
| a small business owner | (business owner who is physically small) |
| a heavy-metal detector | (device to detect heavy metals) |
| a heavy metal detector | (metal detector that is heavy) |
When in Doubt
Apply the clarity test: if removing the hyphen could cause confusion, keep it.
Compound Adjectives with Color
Color compounds follow specific patterns based on their relationship.
Color compound adjectives have special rules:
- Hyphenate when combining two colors: blue-green ocean, yellow-brown leaves
- Hyphenate when a color is modified: dark-blue suit, light-green eyes
- Don't hyphenate color + noun combinations: forest green paint, brick red building
Three or More Words
Longer compounds use multiple hyphens to join all parts together.
When three or more words form a compound adjective, use hyphens between all elements:
- a state-of-the-art facility
- a middle-of-the-road policy
- a once-in-a-lifetime opportunity
- an up-to-date report
Common Mistakes to Avoid
Understanding specific pitfalls helps prevent hyphenation errors.
Watch Out For These Errors
1. Don't hyphenate very + adjective:
- Incorrect: a very-large house
- Correct: a very large house
2. Don't hyphenate compound adjectives after nouns:
- Incorrect: The book was well-written.
- Correct: The book was well written.
3. Don't hyphenate proper nouns used as adjectives:
- Incorrect: South-American cuisine
- Correct: South American cuisine