noun, used as a prefix
Used as a prefix in technical or formal compounds, especially in geology, history, and biology, to indicate an old or ancient period or form.
古期造山帯は、古い時代に形成された山脈です。
The old orogenic belt is a mountain range formed in ancient times.
この化石は古期の地層から発見された。
This fossil was discovered in an ancient stratum.