Compound Nouns Exercise (4)
In this exercise, decide whether each compound noun should be styled as open, hyphenated or closed compound, according to Merriam-Webster's Collegiate Dictionary:
Answers and Explanations
Logic is not a reliable factor in how a compound noun is styled; it's best to always look a term up to be sure that you are treating it correctly. Compound nouns often evolve from open to hyphenated to closed, but sometimes the intermediate stage is skipped, and sometimes a term remains open or hyphenated (so far).
1. air conditioner