noun, plural -ties, adjective | 1. | a cardinal number, ten times four. |
| 2. | a symbol for this number, as 40 or XL or XXXX. |
| 3. | a set of this many persons or things. |
| 4. | forties, 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. |
| 5. | amounting to 40 in number. |