• When do you use hyphens in numbers?

Incorrect: There are three-hundred-sixty-five days in a year.

Correct: There are three hundred sixty-five days in a year.

Use a hyphen when writing out the numbers twenty-one to ninety-nine in words. Do not use hyphens for other numbers.


Incorrect: France has a 35 hour working week.

Correct: France has a 35-hour working week.

Incorrect: The ten year old boy wanted to become an archaeologist.

Correct: The ten-year-old boy wanted to become an archaeologist.

Use hyphens only when the number functions as an adjective phrase.