Fell is the past tense of fall. When you say “I fell,” you're describing something that already happened: you dropped to the ground, you tumbled, or you lost your balance. “Yesterday I fell off my bike” tells what occurred in the past, while “I am falling” or “I will fall” describes something happening now or later.

The word works for many kinds of falling. Leaves fell from the trees in autumn. The Roman Empire fell after centuries of power. A heavy silence fell over the classroom when the principal walked in. Prices fell after the holiday sales ended. In each case, something dropped, declined, or came down from where it was before.

You might hear someone say that night fell, meaning darkness arrived gradually but completely, like a curtain falling. Or that a city fell to enemy forces, meaning it was captured or defeated. The word can describe physical falls, like tumbling down stairs, or metaphorical ones, like when someone's confidence fell after a disappointment.