What's the difference between a motor and an engine? (2013)
Debate over the difference between a “motor” and an “engine” quickly broadens into questions of engineering practice, language, and regional usage. Commenters propose competing technical definitions (electric vs. thermal, motion vs. power, subtype vs. superset) while noting that in everyday English the terms are often used interchangeably and map inconsistently to other languages. The thread also touches on how institutions, jargon, and even hobby products shape terminology, and whether prescriptive definitions can or should keep up with evolving common usage.
Scope of the distinction
- Many participants say that in everyday English, “engine” and “motor” are often used interchangeably, especially for car powerplants.
- Others insist they are not true synonyms, especially in technical or engineering contexts.
- Several note that some collocations feel fixed: “jet engine,” “steam engine,” “fire engine,” “search engine,” but never “electric engine.”
Competing definitions
- Energy source–based:
- Common pattern: “engine” burns fuel or uses heat (internal/external combustion, heat engines); “motor” is electrical, hydraulic, pneumatic, or otherwise non-combustive.
- Counterexamples: “rocket motor,” “motorway,” “motorcycle,” many of which involve combustion; so this rule is seen as leaky.
- Function/role–based:
- Some: motor = produces motion/locomotion; engine = produces power/work, possibly not motion.
- Others: engine = self-contained, cyclic system driving a process; motor = specific component converting some energy into kinetic energy.
- Several argue either:
- motor ⊂ engine (motor = engine that changes momentum), or
- engine ⊂ motor (engine = motor that’s a complex heat/combustion device).
- No consensus; many acknowledge their own usage is intuitive and full of exceptions.
Domain-specific usage
- Cars: many say “gas engine” vs “electric motor,” but “motor car,” “motorsport,” “blown motor” remain common.
- Aviation: some mechanics use “engine” and “motor” interchangeably; “jet engine” is standard.
- Marine: “outboard motor,” never “outboard engine.”
- Rockets: one view—solid rockets = motors (no moving parts), liquid rockets = engines (pumps/valves); hobby industry labeling has blurred this.
- Software: “database/game/search engine,” but not “software motor”; French translates “search engine” as “moteur de recherche” (“search motor”).
Cross-linguistic perspectives
- Many languages (French, Spanish, German, Dutch, Italian, Polish, others) largely have a single everyday word that covers both “motor” and “engine,” plus separate terms like “machine” or “Triebwerk” for specific types.
- “Engineer” is linked etymologically to “ingenium” (clever contrivance), tying “engine” historically to “contraption.”
Language evolution and prescription
- Some argue treating older distinctions as binding is “prescriptivist” and unrealistic; actual usage makes them near-synonyms.
- Others strongly resist phrases like “electric engine” and prefer keeping a technical distinction.
- Broader debate branches into how language norms are set (academies vs actual usage), with “literally” cited as an example of long-standing semantic drift.