- a cardinal number, ten times four.
- a symbol for this number, as 40 or XL or XXXX.
- a set of this many persons or things.
- the numbers, years, degrees, or the like, from 40 through 49, as in referring to numbered streets, indicating the years of a lifetime or of a century, or degrees of temperature: His office is in the West Forties. Her parents are in their forties. The temperature will be in the forties.
- amounting to 40 in number.
- the cardinal number that is the product of ten and four
- a numeral, 40, XL, etc, representing this number
- something representing, represented by, or consisting of 40 units
- amounting to forty
- (as pronoun)
