When something disappears, it goes away completely or becomes impossible to see or find. A magician makes a coin disappear from her hand, though it's really hidden somewhere else. When fog lifts in the morning, it seems to disappear into thin air. The sun disappears below the horizon at sunset, only to reappear the next morning on the other side of the sky.

Things can disappear in different ways. Your homework might disappear under a pile of books on your desk (it's still there, just hidden). A puddle disappears as the water evaporates into the air. An entire species can disappear when the last member dies, which is why scientists work hard to protect endangered animals. A person who disappears without explanation can leave everyone worried and confused about where they went.

The word suggests something sudden or mysterious. We don't usually say the snow disappeared if we watched it melt slowly all week. We say it disappeared if we woke up one morning and it was suddenly gone. Disappearance is the noun form: the mysterious disappearance of the cookies from the jar might require some detective work to solve.