a cardinal number, 10 times 3.

a symbol for this number, as 30 or XXX.

a set of this many persons or things.

Printing, Journalism . 30-dash.

thirties, the numbers, years, degrees, or the like, from 30 through 39, as in referring to numbered streets, indicating the years of a lifetime or of a century, or referring to degrees of temperature

He works in the East Thirties. She must be in her thirties. The temperature was in the thirties yesterday.

amounting to 30 in number.