1. the numbers from 50 to 59, especially when referring to temperature, age, or years in a century
Usage: plural form
2. the decade from 1950 to 1959
Usage: plural form; often capitalized as ‘the Fifties’

Examples

• The temperature will be in the fifties today.
• My grandmother is in her fifties.
• He’s somewhere in his early fifties.
• The fifties were known for rock and roll music.
• Fashion in the fifties was very different from today.
• Many classic cars were made in the fifties.
• The high today will be in the mid-fifties.