When a solid turns into a liquid it is called fusion, more commonly referred to as melting. When a material moves from one state of matter into another it is called a phase transition. Fusion is just one of approximately different states that matter can phase through.
Fusion, which can be as simple as melting butter in a pan, is something that is seen almost daily. Outside of fusion, vaporization is one of the most common types of phase transitions. This term process is more commonly known as boiling. Solidification, condensation and evaporation are some of the most commonly known phases and terms that are used. Solidification refers to the freezing process, while condensation is when fog or other vapor moves back into a liquid form. Evaporation maybe one of the least noticed phases, where liquid changes to a gas form over a period time.