21 years old vs 21-year-old (Grammatically Correct)
21 years old vs 21-year-old (Grammatically Correct)
21-year-old is an adjective, while 21-year-old is a noun.
Adjectives aren't plurals, while hyphenated compound adjectives are singular.
Adjectives aren't plurals, while hyphenated compound adjectives are singular.
From this, saying both phrases depends on how you use it sentence-wise.
From this, saying both phrases depends on how you use it sentence-wise.
This also applies when saying you're an 18-year-old, or 18 years old.
This also applies when saying you're an 18-year-old, or 18 years old.
What you choose to add to the statement which structure to use.
What you choose to add to the statement which structure to use.
The “year-old” is usually singular and hyphenated when in an adjective phrase.
The “year-old” is usually singular and hyphenated when in an adjective phrase.
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CLICK HERE to learn more examples and usages of this phrase.