The number equivalent to the product of four and ten; 40. Forty is divisible by eight.
A period or span of forty years; often used in historical or biblical contexts. In ancient traditions, a forty of years could symbolize a generation.
A 40-ounce bottle of malt liquor. He bought a forty from the store for the party.
The decade from 40 to 49 in a century, or the age between 40 and 49 in a person's life (usually in the plural form forties). She was born in the early forties.