Use a dash to indicate a sudden break in continuity or to set off an explanatory, a defining, or an emphatic phrase: The sky grew dark—where were the kids? Dairy foods—milk, cheese, yogurt—are a good source of calcium.
Use a hyphen to join the elements of a compound word or to join the elements of a compound modifier before a noun:
well-wisher
ice-skating rink
fifty-three
college-age students
Use a hyphen to divide a word at the end of a line: Rasputin is one of history's most enig- matic and intriguing figures.