(history) A period of time ranging from part of the 17ᵗʰ century through much of the 18ᵗʰ century, characterized particularly by the importance of logic and reason.

(idiomatic) A period of happiness, peace, prosperity, and/or great progress. / (mythology) The Golden Age.

the time of the Industrial Revolution

the period of life between youth and old age; midlife

of, or relating to middle age; neither old nor young

(historical) A historical period of great accomplishment in a field or a society, usually following, and not quite as favorable as, a golden age, and not unfavorable as an iron age.

Belonging in the Stone Age.

(idiomatic) To reach a specific age where one is legally considered to be an adult. / (idiomatic) To mature, or become fully developed.

The age in which nuclear energy and nuclear weapons were developed.

The era, starting in the mid-1940s, during which nuclear energy was developed, and in which it was thought that all energy would be provided by such sources.