Steam engine and Steam-engine

Steam engine noun - External-combustion engine in which heat is used to raise steam which either turns a turbine or forces a piston to move up and down in a cylinder.

Steam-engine and steam engine are semantically related. In some cases you can use "Steam-engine" instead a noun phrase "Steam engine".

Steam engine and steam-engine are semantically related. Sometimes you can replace phrase "Steam engine" with "Steam-engine", this phrases are similar.