Fusion

The term fusion is often used as shorthand for nuclear fusion, but it is also a general term describing the merging of two or more entities into a single entity. The term "heat of fusion" describes the additional heat energy that is required to convert a solid that is already at its melting point into a liquid at the same temperature.

see also: Nuclear fusion, jazz-rock fusion, Fusion cuisine, cold fusion, Nuclear fission, nuclear weapons, Fusion (comics)