weaken

The constant exposure to salt water began to weaken the iron pillars of the pier.

(Chinese) 长期暴露在盐水中开始削弱码头铁柱的强度。

A severe lack of vitamin C can weaken the immune system and make you prone to illness.

(Chinese) 严重缺乏维生素C会削弱免疫系统，让你容易生病。