infirm

1. ADJ A person who is infirm is weak or ill, and usually old. (常指因年迈而) 体弱的[正式]

...her aging, infirm husband. …她那年迈体弱的丈夫。

2. N-PLURAL The infirm are people who are infirm. 体弱者

We are here to protect and assist the weak and infirm. 我们来这里保护和帮助病弱者。