What is the difference between a Robot and a Machine? At what point does a machine begin to be called a robot?

Is it at a certain level of complexity? Is it when it has software etc?.

For instance: A desktop printer has mechanics, electronics and firmware but it is not considered a robot (or is it). A Roomba has the same stuff but we call it a robot. So what is the difference.

I have always believed that a robot is a robot when it takes input from it's environment and uses it to make decisions on how to affect it's environment; i.e. a robot has a feedback loop.

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    $\begingroup$ This is a philosophical question. You might also like to consider thinking about what is the difference between a robot and a living creature. But unfortunately this kind of questions is not constructive for this website. And short answer to your question is that there is no exact definition. $\endgroup$ – Shahbaz Jul 25 '13 at 16:39
  • $\begingroup$ I wouldn't say that this is so abstract/philosophical as the defining the difference between robots and living things. Essentially, this question is asking why a servo doesn't count as a robot even though it senses and reacts to its environment with some goal -- however simple that goal (of holding a position) might be. There is an objective answer to this question, even if it's just to say "what we call a robot is arbitrary". $\endgroup$ – Ian Jul 25 '13 at 17:22
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    $\begingroup$ @Shahbaz, This can't be philosophical; We don't just call any random machine a robot! There must be some sort of criterion. The word robot just means worker anyway so technically human labourers are robots. $\endgroup$ – user797 Jul 25 '13 at 18:11
  • $\begingroup$ Not sure whether this is on-topic here, but will leave open for now... $\endgroup$ – Andrew Jul 29 '13 at 9:29
  • $\begingroup$ @Kurtnelle - I was responding to the Close vote... $\endgroup$ – Andrew Jul 29 '13 at 11:34

You asked two (root) questions:

Question: What is the difference between a Robot and a Machine?


Question: At what point does a machine begin to be called a robot?

If I may, allow me to present the following text to address the first question:

The six classical simple machines

Reference: https://en.wikipedia.org/wiki/Simple_machine

  1. Lever
  2. Wheel and axle
  3. Pulley
  4. Inclined plane
  5. Wedge
  6. Screw

Any one of these “machines” is a long way from (but may contribute to the construction of) a robot.

Addressing your second question and although fiction, Isaac Asimov presented a line of thought (reference: http://en.wikipedia.org/wiki/Three_Laws_of_Robotics) still discussed today:

The Three Laws of Robotics (often shortened to The Three Laws or Three Laws) are a set of rules devised by the science fiction author Isaac Asimov. The rules were introduced in his 1942 short story "Runaround", although they had been foreshadowed in a few earlier stories. The Three Laws are:

  1. A robot may not injure a human being or, through inaction, allow a human being to come to harm.
  2. A robot must obey the orders given to it by human beings, except where such orders would conflict with the First Law.
  3. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

Since I’m referencing Wikipedia verses presenting any original thought, I might as well continue: (reference: http://en.wikipedia.org/wiki/Robot)

A robot is a mechanical or virtual agent, usually an electro-mechanical machine that is guided by a computer program or electronic circuitry. ... Robotics is the branch of technology that deals with the design, construction, operation, and application of robots, as well as computer systems for their control, sensory feedback, and information processing.

In summary, a machine can be a robot, a robot can be a machine, a robot can be virtual. I agree with the poster who said it would be several doctoral programs defining the difference. :)

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    $\begingroup$ @Shahbaz As nice as your re-formatting appears, personally I do not approve of "slick" modifications to URL's. In my original text, the URL was displayed intact as the reference, my choice of display. Thank you for the "brown box" formatting. :) $\endgroup$ – JoeFromOzarks Aug 4 '13 at 19:17
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    $\begingroup$ I was wondering what expression "brown box formatting" is that I'd never heard before, then I realized you are referring to the block quotes! :D Anyway, I didn't mean to offend you. Often the full URL is unnecessary since the link is clickable, hovering over it gives you the address and you can always look at the source anyway. But of course in the end it's your choice. $\endgroup$ – Shahbaz Aug 5 '13 at 0:48
  • $\begingroup$ I did not intend to offend you, I apologize if I did. Regarding the URL masking, I'm just an old guy who prefers to see links intact, and then, I still perform a mouser-over to verify the "shown link" is actually the provided link. Please do not stop editing as you do, it's a valuable addition to the forum. Also, I truly appreciate your contributions, I enjoy reading your posts. $\endgroup$ – JoeFromOzarks Aug 5 '13 at 2:04

As @Shahbaz points out this is a highly philosophical question though it does get to the core of the field of robotics. Dr. John Hollerbach begins his Intro to Robotics notes as follows:

What is a robot? In 1980, the Robot Institute of America (RIA), an industrial trade group, came up with the following definition:

"A robot is a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks."

These days, this definition would be considered too restrictive, as it reflects the concentration of the RIA on robot manipulators on an assembly line. Robotics has broadened over the years in many ways: to include mobility platforms, to address the service sector as well as the manufacturing sector, and to incorporate man-machine interactions, not just autonomy, in telerobotic and virtual reality systems.

Ultimately he does not offer an alternative definition outright, that I recall. Instead he discusses the elements of a robot system which he lists as:

  • Mechanical Structure
  • Actuators
  • Sensors
  • Computer Controller

It is arguable whether the computer controller is even necessary because mechanisms can be built that respond to environmental stimuli without the explicit aid of a computer (see Dr. Robert Full's work). In AI we call such things reflex agents.

If we accept the first three elements (or all four) then our world is overrun by robots. This is a bit unsatisfying for many because we often envision the robots from SciFi. If we don't then the definition becomes arbitrary as @Ian points out because we cannot draw a distinction between two devices with the same components wherein we call one a robot (e.g. 3D printer) and another we don't (e.g. microwave) as you implicitly observe.

Regardless it is generally accepted that these are the elements of a robot. This of course gives rise to the question, did we have robots before we had the term "robot?" The answer to this question is yes (see What is the earliest concept of a robot?). However you shouldn't let this bother you, it is not uncommon for a field of research to come after the technology and/or ideas that define it.

  • $\begingroup$ So we're down to: A multifunction, repurposable machine which responds to environmental stimuli? $\endgroup$ – user797 Jul 25 '13 at 19:11
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    $\begingroup$ I don't know. It seems to me that a 3D printer has one purpose and function, to print 3D objects. Yet most of us here still consider it to be a robot. $\endgroup$ – DaemonMaker Jul 25 '13 at 19:22

In the industrial world, robots have a clear definition to differentiate them from other industrial machines:

Industrial robot as defined by ISO 8373:

An automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications.

Reprogrammable: whose programmed motions or auxiliary functions may be changed without physical alterations;

Multipurpose: capable of being adapted to a different application with physical alterations;

Physical alterations: alteration of the mechanical structure or control system except for changes of programming cassettes, ROMs, etc.

Axis: direction used to specify the robot motion in a linear or rotary mode

The important words in this definition are "reprogrammable" and "multipurpose."

For example, let's think about a welding operation that takes place in a car factory. This operation could be done with a custom machine that lowers welding elements into place at the appropriate place on the car. Or we could install a robot arm, put a welder on the end of the arm, and teach (program) it where to weld. When a new model of car comes along, we can teach it the new weld points. If we no longer need the welding operation, we can move the robot somewhere else, put a new tool on the end of the arm, and teach it to paint or to screw in a bolt.

In a larger context, people have different ideas about what is a robot and what is not. But "multipurpose" and "reprogrammable" are still key ideas. If you can't easily re-purpose your machine to do something completely different by reprogramming (and perhaps making minimal hardware "tool" changes), it's not a robot.


When I was contributing to the Robot Wikipedia article, this was a question I spent a long time struggling with. What could you possibly write in the first sentence to basically define 'robot'. I spent days searching for people's personal definitions of robot, and reading forum discussions, until I found the 'agent' definition, and I realised this was the closest I was going to get to a definition.

A robot is a mechanical or virtual artificial agent

The sense of agency seems to be key whether or not people generally call a machine a robot. A machine must give a sense that it has its own agency:

  • it's active in the environment
  • it can take in data
  • it can affect the environment
  • it has its own internal state

This is why software agents get called robots too, even though they have no body. Software agents are active in the environment inside computers.

A long time ago, the Wikipedia article went into much more depth describing how, for example, Kitt would be considered a robot, while a radio controlled humanoid would generally not be. See the Robot page from July 2009. (Sadly, since then it has rotted quite a lot.)

I think that the reason the 'agency' definition works well is that it replaces the poorly defined and poorly understood concept of 'robot' and replaces it with the equally poorly defined, but much better understood concept of 'agency'. Even if we don't explicitly think of animals and robots as agents, we are wired to recognise agents, and categorise objects into things that are and aren't agents. We can easily tell the difference between animals and plants (well, for the types of animals and plants we usually encounter).

  • Animal -> Robot
  • Plant -> Machine
  • $\begingroup$ Dammnit, I can only +1 this $\endgroup$ – YetAnotherRandomUser Nov 25 '18 at 22:18

There are quite some definitions (see other questions) and even robot ontologies. I am with Joseph Engelberger (inventor of the first industrial robot Unimate):

I can't define a robot, but I know one when I see one.

Works quite well.


Back to the original question, a robot is something that turns it self on and off and does its thing without human interference, touching, sending a signal, ect. Like the Roomba. Sure sometimes you tell it to do certain things, but that is different, that is just for an occasion.When you are done, it goes back to vacuuming again. A machine is a thing that has mechanics, electronics and firmware, but needs human interference to work, like the printer. You send a signal telling it to print, not it telling itself to print. Does that answer your question?

  • $\begingroup$ In other words, you select a goal and a robot can autonomously reach it, while a machine needs guidance. Did I understand your classification correctly? $\endgroup$ – Shahbaz May 22 '14 at 15:04
  • $\begingroup$ If that is the case, is an intruder alarm system a robot? You set a goal for it, "fire an alarm if intruder detected", and it automatically does it. I don't think anyone calls that a robot, though. $\endgroup$ – Shahbaz May 22 '14 at 15:06

A machine is just a device which is defined to do a particular task whereas a robot can execute any task given to it through programming

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    $\begingroup$ Hi and welcome. Your answer is a bit short. Please take a look at the other answers to get an idea of how you could expand upon your answer. $\endgroup$ – Greenonline Oct 22 '18 at 15:03