Mortal means certain to die eventually. Every human, animal, and plant is mortal because nothing lives forever. The opposite is immortal, which means living forever and never dying.

When people describe themselves as mere mortals, they're acknowledging human limitations. A student might say “I'm only mortal” after making a mistake on a difficult test, meaning even though they tried their best, they're not perfect. The phrase recognizes that being human means having limits: we get tired, we make mistakes, and we can't do everything.

The word also appears in mortal danger or mortal enemy. Mortal danger means a threat that could kill you, like a serious injury or another life-threatening situation. A mortal enemy is someone who wants to destroy you completely, not just beat you in a game or argument. In stories, heroes often face mortal enemies who threaten not just defeat, but destruction.

In ancient Greek and Roman myths, gods were immortal while humans were mortal. This difference mattered tremendously: gods could take risks humans couldn't because they'd always recover. Many myths explore what it means to be mortal and why a limited life might actually be more meaningful than an endless one. The Greek hero Achilles chose a short, glorious life over a long, forgettable one, showing how mortals think differently when time matters.