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gigayear

n. A billion (109) years

Usage examples of "gigayear".

It rotates once in thirty-two hours, which is endlessly, subtly disturbing to organisms evolved through gigayears of a quicker rhythm.

Sunniva was cooler gigayears ago, when the first life developed there, and evolution kept pace with the slow warming, but today the planet is at the inner edge of the habitability zone.