thirty · number /ˈθɜrt̬.i/Full view
A2 the number 30
Dictionary examples:

twenty, thirty, forty

She got married when she was thirty (years old).

Learner example:

It's thirty years old. (Key English Test; A2; Italian)

(be) in your thirties/30s
B2 to be aged between 30 and 39
Dictionary example:

Most of my friends are in their thirties.

Learner example:

He was in his thirties and really handsome. (First Certificate in English; B2; Spanish)

the thirties/'30s
B2 the years 1930 through 1939
Dictionary example:

They moved to Paris in the thirties.

Learner example:

In the beginning of the thirties in [the] USA the film industry [grew]. (First Certificate in English; B2; Spanish)

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