Photo: Dodge. Text added by David Tracy.

Many of my friends find it strange when I talk about my Jeep’s 4.0-liter “motor,” as they think that term is reserved only for electric cars. But that’s not true. The terms “motor” and “engine” can technically be used interchangeably.

You’d know this if you grabbed your favorite dictionary and just looked the two terms up. NASA’s online “Dictionary of Technical Terms for Aerospace Use” considers the two terms synonyms. But if an old-school paper dictionary is more your speed, I’ve got an American Heritage College Dictionary in front of me, and it defines engine as: “A machine that converts energy into mechanical force or motion.” It also defines motor as: “Something, such as an engine, that produces or imparts motion” or “A device that converts any form of energy into mechanical energy, as an internal-combustion engine.”

Advertisement

The dictionary specifically mentions the internal combustion engine as a type of motor, so that should settle that whole discussion. And if it doesn’t, consider the fact that the term for “engine” in other languages is actually “motor.” For example, if you translate the term “diesel engine” into German, you’ll notice that their word for it is “Dieselmotor.” Plus, if you look at any old advertising for American car companies at the turn of the 20th century, you’ll likely see the term “motor” used more often than “engine.” (Not to mention, we call a bicycle with an internal combustion engine a *motor*cycle).

So yes, a fossil-fuel powered engine is a motor. And it’s totally OK to call it one.

Photo: Tesla

It’s a lot less common to call an electric motor an engine. Even though the aforementioned paper dictionary defines an engine as a machine that turns energy into motion, it does append that definition 1a with a definition 1b: “Such a machine distinguished from an electric, spring-driven, or hydraulic motor by use of a fuel.”

Advertisement

A number of other dictionaries define the term similarly, specifying that an engine usually involves the consumption of fuel. So yes, even if you can call an electric motor an engine, it’s fairly unusual these days to do so.

To look at this further, have a look at one of MIT’s “Ask An Engineer” columns entitled “What’s the difference between a motor and an engine?” In it, the author talks with Mary Fuller, an MIT literature professor, about the history of the two terms. The story says “motor” comes from the Latin term movere, which means “to move,” and that—while it initially referred to the actual force causing something to move, it was later used in reference to “the person or device that moved something or caused movement.” Fuller says in the story:

“As the word came through French into English, it was used in the sense of ‘initiator...A person could be the motor of a plot or a political organization.”

The article goes on, discussing how the term morphed in time, eventually landing at its current usage:

By the end of the 19th century, the Second Industrial Revolution had dotted the landscape with steel mills and factories, steamships and railways, and a new word was needed for the mechanisms that powered them. Rooted in the concept of motion, “motor” was the logical choice, and by 1899, it had entered the vernacular as the word for Duryea and Olds’ newfangled horseless carriages.

Photo: Frank Augstein

MIT’s story mentions that the term “Engine” comes from the latin word ingenium (which can mean nature, innate character or talent). Eventually, the author says, after “engine” was translated from French to English, it took on the meaning “ingenuity, contrivance, and trick or malice,” and in the 15th century it referred to certain types of physical devices—particularly, Fuller says, things like “an instrument of torture, an apparatus for catching game, a net, trap, or decoy.”

You can learn about the history of the term “engine” by reading this Oxford English Dictionary article. But here’s the gist:

Over a 500-year period...engine had completed a shift from its original abstract meaning of ingenuity, to be applied to simple tools and implements, then complicated machinery with many moving parts, and finally to the part of a vehicle which gives it motion. 

So “engine” has meant a heck of a lot of things over the years, and really morphed towards its current meaning with the advent of the steam engine. By the beginning of the 19th century, MIT writes, both engine and motor honed in on the same meaning, namely “a mechanism providing propulsive force.”

Advertisement

So yes, you can totally say a gasoline-powered car has a motor, and you can say an electric car has an engine, but there’s no doubt that the latter is bit odd, while the former is totally normal.