Hyphenated is the form that tells you the joining has already happened, or that a word is written with a hyphen in it. A hyphenated name has that little dash in the middle, like a double family name. A hyphenated word is one the writer chose to join that way — ice-cream in older spelling, for example. People also stretch it: a hyphenated identity is a picture-word for belonging to two groups at once, as in Taiwanese-American. The verb sense is simple too: if you hyphenated the title, you put the dashes in. Though actually, what counts as hyphenated changes with time. Words that were hyphenated fifty years ago are often one word now, and two writers may not mark the same word the same way.