hyphen

A hyphen is one-half the size of an en-dash (–) and one-third the size of an em-dash (—).

1.  Hyphens are used primarily to make compound words, especially phrasal adjectives preceding the nouns they modify—for example:

Thou fair-haired angel of the evening . . .

Talking in a sing-song drone . . .

. . . a starch-filled potluck of goodness.

No hyphen is used in an adjective phrase beginning with an -ly adverb—for example:

. . . that I had realized the goal of her poorly conceived plan.

According to strict hyphen usage rules, this is incorrect:

Such advertisements are categorized by sparsely-dressed women . . .

2.  Hyphens help distinguish between homographs with vastly different meanings—for example: co-op instead of coop; re-create instead of recreate.

3.  Hyphens are occasionally used in compound nouns, although usage varies, and specific conventions govern each case. Invented compound nouns are usually good candidates for hyphenation; poets often do this with whimsical coinages—for instance:

And the flags where the butter-bump hides in for ever . . .