Compound Adjectives: correct answers
Jump to answers ↓What is a Compound Adjective?
A compound adjective is created when two or more words work together to describe a single noun. To show the reader that these words act as one linked idea, we connect them with a hyphen.
If we don't use a hyphen, the sentence can become confusing because the reader might think the words are separate adjectives.
✅ Try our new sugar-free cookies! ❌ Try our new sugar free cookies.
By writing sugar-free, we make it clear that the cookies contain zero sugar, rather than being "free cookies made of sugar." Other common examples include ice-cold lemonade, open-plan living room, and world-famous pool.
Number + Noun Combinations
One of the most common types of compound adjectives combines a number and a noun. When this combination comes directly before another noun, two things must happen: you must use a hyphen, and the noun inside the adjective must be singular.
Even though the number is plural (like three, ten, or 500), the noun attached to it drops its "s."
✅ We took a three-hour boat ride down the river. ❌ We took a three-hours boat ride down the river.
✅ I have to write a ten-page essay on the history of cheese. ❌ I have to write a ten-pages essay on the history of cheese.
Note: If the measurement comes after the noun, it is no longer acting as a compound adjective. In that case, drop the hyphen and make the noun plural again: The boat ride was three hours long.
The "-ly" Adverb Exception
Not all compound adjectives get a hyphen. A major exception is when the first word is an adverb ending in -ly (like highly, beautifully, or poorly).
Because the -ly ending already clearly signals to the reader that the word is an adverb modifying the next word, a hyphen is unnecessary and grammatically incorrect.
✅ Guests will sleep in beautifully decorated suites. ❌ Guests will sleep in beautifully-decorated suites.
✅ Professor Higgins is a highly respected expert. ❌ Professor Higgins is a highly-respected expert.
Be careful: Adverbs that do not end in -ly (like well, ill, or high) still need a hyphen when they come before a noun. For example, a well-known author is correct, while a highly rated restaurant takes no hyphen.
Before vs. After the Noun
The placement of the adjective changes the punctuation. The general rule is that you only hyphenate a compound adjective when it comes before the noun it describes (attributive position).
If the exact same words come after the noun (predicative position), they usually lose the hyphen. This is a very common error for English learners.
✅ We are selling a well-maintained house. (Before the noun = hyphen) ✅ The house is well maintained. (After the noun = no hyphen) ❌ The house is well-maintained.
✅ She is a well-known blogger. ✅ The blogger is well known. ❌ The blogger is well-known.
When proofreading your own writing, always check where the noun is. If the descriptive words follow a verb like is, are, or seems, you can safely leave the hyphen out.
Correct answers
Question 1
Choose the grammatically correct sentence to complete the student's course review.
The correct answer is Professor Higgins is a highly respected expert in ancient alien theories.
Never use a hyphen in a compound adjective if the first word is an adverb ending in "-ly" (such as highly, beautifully, or happily).
Question 2
The correct answers are We took a three-hour boat ride down the river. and The guide showed us a 500-year-old castle.
When a number and a noun combine to form an adjective before another noun, they must be joined by hyphens (e.g., three-hour, 500-year-old).
Additionally, the noun inside the compound adjective is always singular (e.g., hour, not hours).
Question 3
Today, I finally activated Sparky, my three-legged robotic dog. He is supposed to run on a ten-hour battery charge, but he immediately ran outside and started chasing fast-moving delivery trucks. Now I have to write an apology letter for my neighbor's highly damaged garden gnome!
three-legged: Compound adjectives made of a number and a noun (often with an "-ed" ending) are hyphenated before a noun.
ten-hour: When a number and a noun form an adjective before another noun, the noun in the compound is always singular and hyphenated (e.g., a ten-hour charge, NOT a ten-hours charge).
fast-moving: Adjective + participle combinations are hyphenated when they come directly before the noun they modify.
highly damaged: Never use a hyphen after an adverb ending in "-ly."
Question 4
Help the travel agent complete this luxury vacation brochure by dragging the correct descriptions into the blanks.
Guests will relax by a world-famous pool and sleep in beautifully decorated suites.
Guests will relax by a world-famous pool and sleep in beautifully decorated suites.
Compound adjectives made of a noun and an adjective (like "world-famous") are hyphenated when they come directly before a noun.
But remember the golden rule: never hyphenate an "-ly" adverb with a participle or adjective (beautifully decorated)!
Question 5
The correct answers are This is a beautifully decorated home. and The house features an open-plan living room.
We use hyphens to connect words in a compound adjective before a noun (like open-plan).
However, there is a special exception: if the first word is an adverb ending in -ly (like beautifully, newly, or brightly), we never use a hyphen! It should be newly renovated and brightly lit.
Question 6
Select the correct phrase to complete the student's text message to his friend.
I can't come to the party tonight because I have to write a ___ essay on the history of cheese!
The correct answer is ten-page.
When a number and a noun combine to form an adjective before another noun, they must be hyphenated. Additionally, the noun inside the compound adjective is always singular (page, not pages).
Question 7
The correct answers are Try our new sugar-free cookies! and Grab an ice-cold lemonade by the register.
When a noun and an adjective (or participle) combine to describe another noun, they need a hyphen to show they are working together as a single idea.
The incorrect sentences are missing their hyphens and should be written as farm-fresh eggs and mouth-watering chocolate cakes.
Question 8
Help the real estate agent complete the property description by choosing the correct option.
We are selling a ___ house, but the neighborhood itself is not very ___.
The correct answer is well-maintained / well known.
Generally, you should hyphenate a compound adjective when it comes directly before the noun it modifies (a well-maintained house).
However, when the compound adjective comes after the noun, you do not use a hyphen (the neighborhood is not very well known).
Question 9
The hotel boasts a world-famous restaurant, but the main dining room is extremely poorly lit. I ordered a mouth-watering steak, but it was served by a bad-tempered waiter who sighed heavily every time I asked for a glass of water.
world-famous and mouth-watering: When two or more words act together as a single adjective before a noun, they should be hyphenated (e.g., a world-famous restaurant).
poorly lit: Do not use a hyphen when the compound adjective begins with an adverb ending in "-ly" (e.g., poorly lit, beautifully written).
bad-tempered: This is a standard compound adjective. We use the adjective "bad," not the adverb "badly," to form it, and it requires a hyphen before the noun.
Question 10
Complete the travel blogger's post by dragging the correct phrases into the blanks.
We endured a three-hour flight just to visit this highly rated restaurant.
We endured a three-hour flight just to visit this highly rated restaurant.
When a number and a noun form an adjective before another noun (like "flight"), we use a singular noun and a hyphen (three-hour).
However, we NEVER use a hyphen when the compound adjective starts with an adverb ending in "-ly" (highly rated).