If you refer to the fact that people are mortal, you mean that they have to die and cannot live forever.
A man is deliberately designed to be mortal. He grows, he ages, and he dies.
人注定终有一死。长大,变老,然后死去。
You can use mortal to show that something is very serious or may cause death.
The police were defending themselves and others against mortal danger.
警察在保卫自己和其他人免遭致命的危险。
You can use mortal to emphasize that a feeling is extremely great or severe.
When self-esteem is high, we lose our mortal fear of jealousy.
当自尊心很强时,我们不会再对嫉妒感到极度恐惧。
mortals
You can describe someone as a mortal when you want to say that they are an ordinary person.
Tickets seem unobtainable to the ordinary mortal.
普通大众根本买不到票。