A savior is someone who rescues others from danger, harm, or a terrible situation. When a lifeguard pulls a drowning swimmer to safety, that lifeguard is acting as a savior. When firefighters carry people out of a burning building, they become saviors to those trapped inside.

The word carries a sense of serious rescue from something truly threatening or destructive. You wouldn't call someone a savior for helping you find a lost pencil, but you might use the word when someone prevents real disaster. A doctor who discovers a cure for a dangerous disease could be called a savior by the patients whose lives are saved by that cure.

In Christianity, Jesus Christ is called the Savior because Christians believe he saved humanity from sin and death. This religious meaning is probably the most common use of the word with a capital S. You'll encounter this meaning in churches, religious books, Christmas carols, and conversations about Christian faith.

The word can sometimes be used less seriously, almost playfully. If your friend brings you lunch when you're starving and forgot your wallet, you might joke, “You're my savior!” But even then, there's a sense that the person arrived at just the right moment to prevent something bad from happening.