Do compound words have hyphens

While it's true that some compound Words have hyphens, all compound Words do not. For example, the Words horsefly, chestnut, and birdhouse are compound Words, yet they don't have hyphens. On the other hand, a few Words have hyphens, but are still compound Words.

A common rule in determining whether a compound Word should be one Word or two is how the Word is used in context. Phrases that have a verb/noun or verb/adjective combination should be two Words if the combined term is a verb and one Word if the compound Word is a noun or description. For instance, "my car will never break down" uses "break" as a verb, whereas "Michael had a breakdown" uses "break" as part of a noun. This is useful in determining the difference between one and two Word compound phrases, but does not really help us with whether to hyphenate compound Words or not.

One usually consistently hyphenated form of compound Words are those with a connecting middle Word. Terms such as merry-go-round or mother-in-law are almost always written with a hyphen. One exception is commander in chief, which is frequently seen without the hyphen, especially when referring to the President of the United States as an alternate title.