The puddle vanished. Its water had more than one way out.

An empty patch is only the beginning

Imagine returning to a path after rain and finding a dry patch where a puddle had been. The everyday explanation is that the water disappeared. As an observation, that is understandable: the visible pool is gone. As an account of what happened, however, it leaves nearly every interesting question open. The water may have taken several routes rather than one.

Evaporation is one possibility. The US Geological Survey describes it as the change from liquid water to water vapor. It does not require a puddle to boil. Water can leave an exposed surface under ordinary conditions, becoming part of the atmosphere even though you no longer see it as a pool. The lack of a rising plume does not rule out that route.

Condensation works in the opposite direction, turning vapor into liquid. Droplets on the outside of a cold glass offer a familiar example: the glass need not be leaking. Water already present in the surrounding air can collect on its cold surface. That small observation helps separate a change of location from a change of state.

These examples are illustrations of processes, not a measurement of the particular puddle imagined here. To find out how much water evaporated, you would need more information than a before-and-after glance. The ground creates another possible exit, and understanding that exit requires following the water below the part of the landscape you can easily see.