All but one of the following sentences require hyphenation between two or more consecutive words to indicate that the phrase is a phrasal adjective; revise the sentences as necessary:
1. It was in my post office box.
2. The project finances construction of energy efficient homes.
3. The figures above reflect cost of living adjustments.
4. She is still developing her expository writing skills.
5. Images must have high quality resolution.
Answers and Explanations
Phrasal adjectives are strings of two or more words that together modify a noun. When a phrasal adjective precedes the noun, the component words are generally hyphenated to clarify their interrelationship.
Original: It was in my post office box.
Correct : It was in my post office box.
“Post office” is one of many permanent compounds — noun phrases so well established that confusion is considered unlikely and that are therefore not hyphenated when they combine to modify a following noun. (Permanent compounds are listed in dictionaries.) This sentence is correct.
Original: The project finances construction of energy efficient homes.
Correct : The project finances construction of energy-efficient homes.
This sentence refers to homes that are energy efficient, not efficient homes that are energy.
Original: The figures above reflect cost of living adjustments.
Correct : The figures above reflect cost-of-living adjustments.
Here, the sentence does not pertain to living adjustments and their cost; the phrase “cost of living” modifies adjustments.
Original: She is still developing her expository writing skills.
Correct : She is still developing her expository-writing skills.
Skills in expository writing, rather than writing skills that are expository, are the topic of this sentence.
Original: Images must have high quality resolution.
Correct : Images must have high-quality resolution.
This sentence concerns resolution of high quality, not quality resolution that is high.