Compound adjectives, compound adverbial phrases, and compound nouns
Re the “long-sleeved shirt” phrase: this is an example of a compound adjective. It is almost always hyphenated, no matter where it is placed in the sentence:
I have a long-sleeved shirt.
My shirt is long-sleeved, not sleeveless.
Compound adjectives modify the noun following. In the example above, it isn’t a long shirt, it isn’t merely a sleeved shirt, it is a long-sleeved shirt. If the compound adjective is separated from the noun that it modifies, it is hyphenated to avoid ambiguity. Note how the meaning of the following can be misunderstood:
I have long-tangled hair.
I have long tangled hair.
Do I mean that my hair has been tangled for a long time, or do I mean that my hair is both long and tangled? Using the hyphen removes the ambiguity from the sentence.
However, some words have gone from possibly being hyphenated at one time to being one unhyphenated word. “Bulletproof” is one example; it doesn’t matter where it falls in the sentence:
I have a bulletproof vest.
My vest is bulletproof.
Compound adverbial phrases are only hyphenated when they immediately precede the modified noun AND when the adverb is not an “ly” adverb (“ly” adverbs are never hyphenated):
He is a well-known actor.
He is well known.
He is a highly qualified doctor
He is highly qualified.
Certain other adverbs, such as “very” or “pretty” (when used as an adverb) are also not hyphenated when part of an adverbial phrase, even when immediately preceding the noun:
That is a very leafy tree.
That’s a pretty rotten way to treat someone.
Compound nouns are sometimes hyphenated, sometimes not. It is not necessarily incorrect to hyphenate, and sometimes doing so will, again, avoid ambiguity.
She had a breast reduction.
She had breast-reduction surgery.
She had breast reduction surgery.
Some compound nouns are hyphenated all the time. Others used to be hyphenated but have over time become either two separate unhyphenated words or one unhyphenated word. It is best to check a dictionary to make sure. Most of the “self” words (self-esteem, self-employment) are always hyphenated. “Bull’s-eye” is hyphenated, but “bull snake” is two separate words and “bullwhip” is one unhyphenated word. I think compound nouns can be the most confusing, so I just look them up if I’m not sure about it. (These are according to Merriam Webster’s Collegiate Dictionary, 10th Edition.)

