Gas-engine and Internal-combustion engine

Internal-combustion engine and gas-engine are semantically related. In some cases you can replace phrase "Internal-combustion engine" with "Gas-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.

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