Motor Vs. Engine — What’s The Difference?

At the risk of starting an internet fight of epic proportions, we’re going to tackle one of the largest debates the automotive world has ever seen: motor vs. engine. While it might seem as easy as simply picking up a dictionary, the chances are, you couldn’t find a good, old-fashioned, 1,000-page brick within 30 seconds in this day and age. That issue has created some issues in and of itself in this debate.

In order to cite our sources, we’ll need to use the online version of the more commonly accepted dictionaries. The problem is, when those definitions don’t match someone’s argument online, the quickest answer is to dismiss their validity because they are online. Rather than face that someone’s preconceived notion might be incorrect, the more reasonable solution to some is that an established dictionary company has thrown its centuries of ethics and morals out the window simply because the medium of publishing has changed.

The Real Definitions

Below, we’ll list the definitions of motor vs. engine from three of the most reputable dictionaries we can access for free. (Note: the formatting oddities are specific to each publication. We left them in the original formatting as published as much as possible, so we aren’t accused of skewing the information.)

Merriam-Webster Dictionary – First published 1828

Engine:
1: a machine for converting any of various forms of energy into mechanical force and motion
also : a mechanism or object that serves as an energy source

Motor:
1: one that imparts motion
specifically : PRIME MOVER
2: any of various power units that develop energy or impart motion: such as
a: a small compact engine
b: INTERNAL COMBUSTION ENGINE
especially : a gasoline engine
c: a rotating machine that transforms electrical energy into mechanical energy
3: MOTOR VEHICLE
especially : AUTOMOBILE

American Heritage Dictionary – First Published 1969

Engine:
1.a. A machine that converts energy into mechanical force or motion.
b. Such a machine distinguished from an electric, spring-driven, or hydraulic motor by its use of a fuel.

Motor:
1. Something, such as a machine or an engine, that produces or imparts motion.
2. A device that converts any form of energy into mechanical energy, especially an internal-combustion engine or an arrangement of coils and magnets that converts electric current into mechanical power.
3. A motor vehicle, especially an automobile.

Collins English Dictionary – first published 1979