gas to liquid is called

Gas turning into a liquid is called condensation.

In school-level chemistry and physics, when a substance in the gas state is cooled (or compressed) enough that its particles come closer together and form a liquid, that phase change is specifically named condensation. A familiar example is water vapor in the air forming liquid water droplets on a cold glass or as clouds and rain in the water cycle.

In industrial contexts, there are also specialized “gas-to-liquid” (GTL) processes that convert natural gas into liquid fuels, but for a simple states- of-matter question, the correct term is condensation.