The decade of the 1850s, 1950s, etc.
The decade of one's life from age 50 through age 59.
(temperature, rates) The range between 50 and 59.
It can't snow tonight; it's forecast to be in the fifties!
From or evoking the 51st through 60th years of a century (chiefly the 1950s).
A banknote or coin with a denomination of 50.
Do you want small bills or are fifties OK?
A batsman's score of at least 50 runs and less than 100 runs.