Use a hyphen when writing two-word numbers from twenty-one to ninety-nine (inclusive) as words. But don't use a hyphen for hundreds, thousands, millions and billions.
Are numbers hyphenated when written out?
NUMBERS: from twenty-one to ninety-nine, when spelled out, are hyphenated. FRACTIONS: Hyphenate a fraction when it is used as a adjective (e.g., a two-thirds majority). Write as two words when used as a noun (e.g. two thirds of the participants).
How do you hyphenate a 21 year old?
Summary: When to Hyphenate Year Old
- Hyphenate when expressing ages as adjectives before a noun or as substitutes for a noun. The 21-year-old woman gave a presentation.
- Do not hyphenate when simple stating the age of something or someone. He is 26 years old.
