|Origin:||thritig, from thrie 'three'|
the number 30
2 [plural] also the '30s, the 1930sTMC
the years from 1930 to 1939:
In the thirties, air travel really began to take off.
the early/mid/late thirties
The family sold the house in the early thirties.
to be aged between 30 and 39
She must be in her early thirties by now.
if the temperature is in the thirties, it is between 30 degrees and 39 degrees
in the low/mid/high thirties
a hot day, with temperatures in the low thirties
—thirtieth adjective, pronoun:
her thirtieth birthday
I'm planning to leave on the thirtieth (=the 30th day of the month).