(fifties)
Frequency: The word is one of the 700 most common words in English.
1.
Fifty is the number 50.
NUM
2.
When you talk about the fifties, you are referring to numbers between 50 and 59. For example, if you are in your fifties, you are aged between 50 and 59. If the temperature is in the fifties, the temperature is between 50 and 59 degrees.
I probably look as if I’m in my fifties rather than my seventies.
N-PLURAL
3.
The fifties is the decade between 1950 and 1959.
He began performing in the early fifties.
N-PLURAL: the N