depth什麼時候加s

depth在中文意思是n. 深處深淵的時候加s，變成複數。

Marine life was discovered at depths previously thought to be azoic.在先前被認為沒有任何生命跡象的海洋深處發現了海洋生物。

Now she was dredging up memories from the depths of her mind.

這時，她回憶起內心深處的往事。