What is the difference in meaning between a robot, a machine, and an automaton? I was inspired to ask this because I really can’t understand the subtle (or not so subtle) difference in meaning here.

  • I believe that robot is something that can operate on its own with AI (artificial intelligence).
  • An automaton is something like a black box: if we enter A, we know we will receive B (although we have no idea why).
  • Machine is everything mechanical.

What brings all this to my attention, and that maybe my understanding about the meanings of these three words is wrong, is this question.

  • What's wrong with looking these words up in a dictionary, to see what they mean?
    – Drew
    Feb 28, 2016 at 16:15
  • It utterly depends on context. To a physicist or a mathematician the meanings are very different from those in a science fiction novel.
    – Stuart F
    Mar 23, 2022 at 10:42

6 Answers 6


This is going to be a tricky question to answer, because all three words can be used in a wide range of contexts.

A robot is something mechanical that does something useful. In science fiction, robots often take on humanlike qualities, but robots can in fact be much simpler than that (e.g., a vacuuming robot).

An automaton is something that performs some task in accordance with some preset instructions. Some dictionaries describe automata as a synonym for robot, but the term is also used in a more abstract sense in a branch of mathematics. The emphasis is, once built, the automaton can keep doing what it's supposed to be doing without further intervention.

A machine is something mechanical that makes some task easier (e.g., a sewing machine, a washing machine). Usually, emphasis is on something mechanical, although, like automaton, this word is applied to more abstract machines as well.

So, your description is correct: there is much overlap between the words, so much so that they can often be used interchangeably.

  • 1
    "These aren't the automatons you're looking for..."
    – Polynomial
    Jun 8, 2012 at 12:59
  • In case you are reading older texts, it's also worth bearing in mind that "robot" is a relatively new term. At the beginning of the 20th century, what we now describe as a "robot" would probably have been described as an "automaton" in the absence of a more specific term. Jun 8, 2012 at 16:53
  • 1
    Finite automata are robots with an expiration date, like the replicants on Blade Runner. :)
    – tchrist
    Jun 8, 2012 at 19:07

Even though it has been greatly responded, it's a very interesting question to me and I would like to bring some few more elements.

In short, I would say that there is a very strict hierarchical order between the three terms. Robots are specific types of automata, automata are specific types of machines (which are a specific types of systems).


Nowadays, a machine is an invented system (by humans, as far as I know), with an intended behavior (more or less definite, with various degrees of freedom), given by a set of mechanisms that determine some actions (changeovers between states). One can trigger some actions, toggling states, by interacting with the machine, using it's mechanisms (well, the interfaces to its mechanisms actually, but whatever).

It's very general, and ontologically, I would oppose it as natural systems* ("natural" in the common sense). I would almost say that in a regard, a machine is a prescriptive system, while others are descriptive systems, since our knowledge about the latter as systems only comes from what we can detect and describe about the actual phenomena, while the behaviors of the former are (or should be almost) completely ruled by some inventors.

Machines can be physical*, or theoretical.

some examples: the nervous system, the water cycle, even the financial system (which is not that "natural", but it still is pretty much a self-organizing system), or the way ants find the shortest route up to some resources, are natural systems*.

Traditional sewing machines (non electrically powered), boilers, combustion motors, windmills or automatized machines like washing machine or industrial robots, etc., are physical machines*.

Abstract machines (lambda-calculus, Turing's machine, regular expressions, etc.), programming languages, or some theoretical systems in some formal sciences (e.g. natural deduction) are theoretical machines. They are invented systems that provide rules and axioms, mechanisms that allow to do things, just as well as physical machines*.

some related words: device, apparatus, machination, mechanism, machinery


An automaton is a machine that has some automatic behavior, a self-operating machine. Basically, it takes in input an input sequence (a program) and do things according to its internal design mechanically, like any other machine, and automatically, according to the program in it's intput. In this regard, it's a machine that has been restricted to be able to self-act following a sequence of instructions.

Really, it's nothing more than an automatic machine. As for machine, it can be physical (washing machine), or theoretical (Turing Machine, Finite State Acceptors, Transducers, and so on, and so forth). Even though automata are way more common since the digital era, there were mechanical automata.

Regarding the theoretical automata, note that what we call Turing Machine is acutally an automata, an universal abstract machine (even though Turing himself described it as an "automatic discrete machine") that takes in its input a (infinite) tape with symbols that constitutes it's sequence of instructions. Finite State Machine (accessors, transducers, and so on) are also theoretical automata.


Now, probably the most controversial, probably because the most recent.

As well as automata, robots ARE machines, because they are systems that have been invented by humans.

Also, robots ARE automata as well, because they are, basically, automatic machines.

But in order to consider robots as automata, we ne to grasp the idea of higher order functions. Because robots are those specific higher-order automata. They are functional automata.

Whether the robots be autonomous or not (remote controlled for instance, or supervised, for virtual robots), we do not say to robots: "switch from this state to this state". What we say to robots is much more something like "do that". And from here, they are self-deciding, whereas automata are just self-acting. We don't say to robots "how to do things". We say them "what to do". This is where "artificial intelligence" comes into the game. We tell them what to do, and they are sophisticated enough to "decide" by themselves how to do actually the things, they choose the best way of changing their internal states regarding the context.

Note that the term itself robot gives a good idea of that. It comes from the Czech robotnik which means slave. Because we dont pilot them step-by-step, we just say them what to do.


That why we do not refer to robots as "cool stuffs with advanced functionalities", as we do with automata, but much more as agents with roles.

In a washing machine, which is an automaton, we put some dirty clothes (parameters), we set a program (input sequence), and it runs the program. At the end, we get some clean clothes (output).

To the Big Dog, we say "follow me", and it figures out by itself how to follow you, whatever be the terrain. But it still is an automaton. A specific higher-order, functional_ automaton.

To an industrial robot (which is controlled by several Programmable Automation Controllers, which get data from various sensors, do the relevant complex computation regarding its internal states, and transmit commands to motors, which convert logical commands to mechanical power), we say "Make a door curtain", and it will takes a new sheet metal, will cut it, bend it, sand it, braze it, control it, and so on. If we say it's an automaton, we are not wrong, we just are under-specified. The same if we say it is a machine.

Automaton is considered as a tool. A cool, sometimes painless tool. Robot is a higher-order tool, intended to make low-level decisions by itself, that's why we say they are agents, not just tools anymore.

Finally, as well as machines and automata, a robot may be non-physical. In the case of robots, we do not say theoretical nor abstract, though, since they always are applied to concrete cases, so we say virtual. Chatterbots, or Web Crawler are virtual robots, also called bots.


If you have some better words for natural system, physical machine, or any suggestion, please don't hesitate to report them because I'm not very happy with that.

  • Stellar answer. +1 Jun 10, 2012 at 20:54
  • I know we're supposed to avoid comments like +1 or thanks, but +1 thanks! This is off the hook Feb 15, 2017 at 13:29

"Machine" is a very general word. Any sort of man-made device that has moving parts can be called a "machine".

"Robot" means a machine that can operate without an immediate human operator. That is, while it must be programmed or somehow given instructions in advance, it can then do its job independently, without anyone working its controls. Originally the idea of a "robot" was that it was at least vaguely human-looking, for example having a basically human shape, such as a head, arms, and legs. But as robots moved from science fiction to reality, people decided it was more practical to make machines that were not necessarily human-looking. So today, for example, automated vacuum cleaners that look like a box or a disk are called "robots" and no one questions it.

Human-looking robots are now called "androids". But then Star Wars came along and used the word "android" to refer to robots that are not very human-looking, and thus may have ruined that word.

"Automaton" means a machine capable of acting independently, i.e. the same as what "robot" means now. Back when "robot" included the idea of human-looking, an "automaton" was a machine that acted independently that did NOT necessarily look human.

So what we used to call an "automaton" we now call a "robot". What we used to call a "robot" we now call an "android".


I'm assuming the context here relates to existing mechanical devices as opposed to science fiction. Machine is the most general of the terms and fits what the OP says. The OED defines machine as: "an apparatus constructed to perform a task or for some other purpose."

OED has the meaning of automaton as "a machine which performs tasks usually associated with human workers." This is different than the OP's supposition that an "automaton is something like black box;" rather it's a specialized machine intended to do human labor and it isn't necessarily programmable.

Robot is "a machine capable of automatically carrying out a complex series of movements, esp. one which is programmable." Here the OP is closer to the mark in saying a robot is "something that can operate on its own," in that programmability is strongly implied.

Of the three terms, it seems that only automaton specifically relates to replicating what people have done.


In this discussion we have a widely variable usage of the English language. Since, of the three, machine is the oldest, it is also the one with the broadest meaning. The original word could mean anything man made. It comes to English from the Greek, to the Latin, to the French and then adopted into English. It could be anything as simple as a fabric or any kind of structure. Today we use it to describe primarily mechanisms with moving parts that perform function. Since it is the oldest term it is also the broadest of the three and includes all automata and robots.

The other two terms are used interchangeably. Here is the derivation and meaning of automaton: "1610s, from Latin automaton (Suetonius), from Greek automaton, neuter of automatos "self-acting," from autos "self" (see auto-) + matos "thinking, animated, ... from the Online Etymology Dictionary, and this from Merriam-Webster: "Full Definition of automaton plural au·tom·atons or au·tom·a·taplay -mə-tə, -mə-ˌtä\ 1 : a mechanism that is relatively self-operating; especially : robot 2 : a machine or control mechanism designed to follow automatically a predetermined sequence of operations or respond to encoded instructions 3 : an individual who acts in a mechanical fashion"

Automata and robots are mecdhanical devices that perform a function or functions by themselves. They can be simple mechanical devices to which power is supplied and a function is provided. Most modern factories use mechanical devices to perform operations that were once done by humans. We speak of automating a process. However, we also apply the term robot and robotics to rote performing mechanisms such as those employed in construction of modern vehicles.

We have broadened the term "robot" to include devices that are directly controlled by humans via tethered or broadcast mechanisms to perform functions we specify by human activity. Examples include drones and surgical equipment where a doctor moves his hands and a mechanism imitates that motion.

A special case of robotics involves forms of parts or all of a human body made to imitate actions performed by actual living creatures and made, either very simply or complexly like people or animals. A nineteenth century automaton that gained widespread fame was Maelzel's chess player. This mechanism was a closed box with a chess board on the top. It would challenge chess players. There was a window below where observers could see moving gears and a mechanical hand would move the pieces. Edgar Allen Poe exposed it as containing a midget who actually caused the motions and played the game.


Robot means to work anything you have done by the operator (human). Machine means to create a motion and force of the system.

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