Gaseous water is called vapours.
The term we use for H2O when it's a liquid is water. The solid form is ice, and in the form of a gas, it's called steam.
When water is in the vapour form of steam, it is in a gaseous state.
The process is called evaporation. It occurs when the sun heats the Earth's surface, causing water to change from a liquid state to a gaseous state and rise into the atmosphere as water vapor.
Water in a gas phase is called water vapor. It is the gaseous form of water and is invisible to the naked eye.
The changing of gaseous water vapor in the air to liquid water is called condensation. If it does so high up in the atmosphere and falls as droplets to the ground we call that "rain" - but it has to undergo condensation first.
Water Vapor Commonly called "Steam"
Water in its gaseous form is called water vapor because it consists of individual water molecules floating freely in the air. "Water gas" typically refers to a different compound, a mixture of carbon monoxide and hydrogen, which is used in industrial processes.
The liquid state of water is called "water."
HCl is called hydrogen chloride when it is in its gaseous form, and hydrochloric acid when it is dissolved in water.
When water evaporates, it changes from a liquid state to a gaseous state, but it remains the same kind of matter - water. The molecules in water are still composed of two hydrogen atoms and one oxygen atom whether it is in liquid or gas form.
atmosphere
The change in state would be known as melting. Just for your information: Solid to Liquid = Melting Liquid to Gaseous = Boiling Solid to Gaseous = Sublimation Gaseous to Liquid = Condensation Liquid to Solid = Freezing Gaseous to Solid = Deposition