This is the 7346th most frequent Japanese word.
人命
Human life.
Here, "人命" refers to the responsibility to preserve human lives in a general sense.
人命を守るのは私たちの義務です。
Protecting human lives is our duty.
In this sentence, "人命" pertains to the specific lives of people that the doctor saved.
その医師は多くの人命を救いました。
That doctor saved many human lives.
Here, "人命" refers to the importance of prioritizing human lives in the context of disaster response.