Hyphens in AgesThis page explains the rules for using hyphens in ages.
Hyphens in ages appear in three forms:
- The compound-noun form; e.g., A twenty-four-year-old paid the first tribute.
- The compound-adjective form; e.g., She is a twenty-four-year-old woman.
- The predicate-adjective form; e.g., She is twenty-four years old.
The "Compound Noun" FormHere are some examples of the compound-noun form:
- He is a two-year-old with attitude. (This is a compound noun. (It is just like words like ice-axe or cooking-oil, which are also compound nouns.) The words in a compound noun are linked together to show they are a singular entity.)
- I look after three two-year-olds from 9 am to 11 am. (As with most nouns, there is a plural version too.)
Read more about compound nouns.
The "Compound Adjective" FormHere are some examples of the compound-adjective form:
- He is a two-year-old horse. (This is a compound adjective. It is no different from word an adjective like two-page in two-page document.
- I look after three two-year-old horses. (As with most adjectives, it can modify something singular or plural.)
Read more about compound adjectives.
The "Predicate Adjective" FormHere are some examples of the predicate-adjective form:
- Jason is two years old. (The predicate-adjective form appears after a linking verb (here, is) and after the noun it modifies (here, Jason). There is no need to use hyphens in the predicate adjective form.)
- Jason is twenty-two years old. (This version contains a hyphen only because twenty-two is spelt with a hyphen under the rules for writing numbers in full.)
Here are some simple rules for using hyphens with ages:
(1) There is never a hyphen after the word old.
(2) There is never a hyphen before or after the word years (Note: This rule applies only to years not year.)
(3) There are always hyphens around the word year (provided it's not in a predicate adjective following a or one).
Of course, someone could concoct an example or two to undermine these rules, but if you're struggling to understand compound nouns, compound adjectives, and predicate adjectives, these rules will see you right.