软弱

例句：

1. 1. The old man was weak from lack of exercise.
   老人由于缺乏锻炼而身体虚弱。
2. 2. Her voice is weak, barely audible.
   她的声音很弱，几乎听不见。
3. 3. The child was so weak that he couldn't walk by himself.
   孩子太虚弱了，走不了路。