Other forms: alleys
An alley is a narrow street with walls or buildings on both sides, like the dark alley everyone warns you not to walk down alone.
Alley comes from the Old French word alee, meaning "a path, passage, way, corridor," which itself likely comes from the Latin word ambulare "to walk." That sums up what an alley is — a street that is usually too narrow for cars, though it is easy to walk there. However, alleys are often associated with danger and crime because they don't have much light shining in them, and it is easy for shady characters to hide.