Heat engine and Internal-combustion engine

Heat engine noun - Any engine that makes use of heat to do work.

Internal-combustion engine and heat engine are semantically related. In some cases you can replace phrase "Internal-combustion engine" with "Heat engine", this phrases are similar.

Internal-combustion engine noun - A heat engine in which combustion occurs inside the engine rather than in a separate furnace; heat expands a gas that either moves a piston or turns a gas turbine.

Heat engine and internal-combustion engine are semantically related. You can use "Heat engine" instead a noun phrase "Internal-combustion engine".