古こ期き

noun, used as a prefix

old; ancient

Used as a prefix in technical or formal compounds, especially in geology, history, and biology, to indicate an old or ancient period or form.

• 古こ期き造ぞう山ざん帯たいは、古ふるい時じ代だいに形けい成せいされた山さん脈みゃくです。

  The old orogenic belt is a mountain range formed in ancient times.

• この化か石せきは古こ期きの地ち層そうから発はっ見けんされた。

  This fossil was discovered in an ancient stratum.