In my answer to the question about the opposite for bug in programming, I referred to 'bug' as a slang word.

Shaun Wilson, in his comment insists on 'bug' being a term that derived from a historical process:

"bug" is not "slang for error", "bug" is a historical term derived from the process of fixing old vacuum tube based computers from yesteryear, where a moth or similar would find its way into the computer causing a short (and an error in programming). Thus the term "debugging" was born, and still, today, we refer to programming errors as "bugs". Often users refer to things as bugs which are not, such as feature changes, or unexpected behaviors which are not bugs (but were otherwise unintended.) This is also why we have a running joke about certain bugs being features

While the above is a great note on the etymology, I still do not agree 'bug' is a term if used in computer programming; the term is something that is singular in meaning, singularity is a property of a term. Something other than one official term may be slang. In case of a live bug in vacuum tube it was the term describing the object literally. In case of computer bug, error is implied, and 'bug' is a figurative description.

So the question is: if a word used to be a term because it described an object literally (real bug), now is used figuratively (computer error), does it remain a term or is it a slang word?

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    It is understood by most people, yes, but it is it used in official documentation?
    – Oleksii
    Commented Apr 14, 2015 at 18:14
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    After more research, I've found the term definitely predates vacuum tubes, so this suspicious etymology is historically INCORRECT. The Oxford English dictionary's earliest citation is from 1889 where the term is used to refer to a problem in a phonograph. The "bug" of the citation is explicitly referred to as metaphorical and not literal: oed.com/view/Entry/24352?rskey=lKGuxd&result=2#eid
    – herisson
    Commented Apr 14, 2015 at 18:23
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    I know the etymological info isn't the main point of this question, but I'll just reinforce that this is not the actual historical origin of the term with a reference to this other English Stack Exchange question: english.stackexchange.com/questions/40934/…
    – herisson
    Commented Apr 14, 2015 at 18:28
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    The metaphorical use of bug to mean a defect in a system, equipment etc. long predates the age of the computer - as the OED makes clear.
    – WS2
    Commented Apr 14, 2015 at 18:37
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    "Debugging" was popularized as a term by Admiral Grace Hopper. See en.wikipedia.org/wiki/File:H96566k.jpg Note the comment "First actual case of a bug being found." Ther term had been in use before in engineering but as a specific term in computing as a distinct enterprise this is usually held as the origin.
    – Wudang
    Commented Apr 14, 2015 at 22:39

4 Answers 4


The story of the real-life moth as a computer "bug" is told at length under the title "First Computer Bug." Even in this case, though, the way the people involved treated the incident suggests that the word bug was already understood metaphorically:

On the 9th of September, 1947, when the machine was experiencing problems, an investigation showed that there was a moth trapped between the points of Relay #70, in Panel F.

The operators removed the moth and affixed it to the log. (See the picture above.) The entry reads: "First actual case of bug being found."

In fact, an instance where bug is used in the sense of "system problem" appears five years earlier than that, in The Autocar: A Journal Published in the Interests of the Mechanically Propelled Road Carriage, volume 87 (1942) [combined snippets]:

I think everyone will agree that there is a "bug" in the system when, in times of peace, poverty can exist amidst plenty. In fact, during a slump, food is actually destroyed whilst hungry people have no jobs and in consequence insufficient money to buy the food that is being destroyed. Under the existing monetary system everyone is fully employed only in times of war! What a system!

Another early use of bug in this metaphorical sense is from United States Investor, volume 61 (1950):

We are neither Republicans nor Democrats ... Protestants, Catholics nor Jews ... white nor black. We are just Americans who believe that the Democratic system is the best there is, but who also know that the system has "bugs" in it that have to be exterminated in order that democracy can come to its full flower of liberty and service for every citizen.

These "bugs" are not the fault of any particular political party or individual. They have developed within the framework of the executive branch of the government, that has, like Topsy, "just growed".

In both of the preceding examples the buggy system was political or economic. But in answer to an EL&U question (Origin of "bug" in reference to software) posed back in September 2011, researcher extraordinaire Hugo noted that bugs is used in a logbook entry from April 17, 1944, at Harvard’s Computation Laboratory (as reported by Peggy Kidwell in an article published in IEEE Annals of the History of Computing (December–October 1998)) in the specific context of computer operation, three years before the much-discussed moth episode:

Ran test problem. Mr. Durfee from I.B.M. was here to help us find “bugs.”

Oxford Dictionaries online finds a much earlier instance of bug—this time in connection with the new technology of audio recording. From "Was the first computer 'bug' a real insect?":

The term in fact originates not with computer pioneers, but with engineers of a much earlier generation. The first example cited in the 20-volume historical Oxford English Dictionary is from the Pall Mall Gazette of 11 March 1889:

Mr. Edison, I was informed, had been up the two previous nights discovering 'a bug' in his phonograph - an expression for solving a difficulty, and implying that some imaginary insect has secreted itself inside and is causing all the trouble.

The upshot is that bug was in use as a metaphorical or figurative term for a systemic problem in 1889. Whether that makes it a slang term more than a hundred years later is a matter of opinion, I suppose—but the notion that prior to the first figurative use of "computer bug," a bug was strictly and literally an insect appears to be incorrect in any case.

  • Can a metaphor or figurative word be considered a 'term' in English? Is metaphor compatible with term?
    – Oleksii
    Commented Apr 14, 2015 at 23:08
  • It can certainly be considered a "term of art"—in the sense that a specific discipline or occupation uses the word in a way understood as having a particular meaning by everyone within that discipline or occupation.
    – Sven Yargs
    Commented Apr 14, 2015 at 23:11
  • Well, the same definition will apply to slang too.
    – Oleksii
    Commented Apr 14, 2015 at 23:12
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    Bug was also used in computing software in 1944, three years before Hopper's 1947 moth: "Ran test problem. Mr. Durfee from I.B.M. was here to help us find 'bugs.'" See english.stackexchange.com/a/41116/9001
    – Hugo
    Commented Apr 15, 2015 at 11:34
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    @Hugo: Excellent find (and answer to the earlier question). I hope you don't mind my adding a reference to your earlier instance of "bug" in a computer setting to my answer.
    – Sven Yargs
    Commented Apr 15, 2015 at 16:41

Was bug literal then figurative?

So the question is: if a word used to be a term because it described an object literally (real bug), now is used figuratively (computer error), does it remain a term or is it a slang word?

For slang, it's irrelevant if something was once literal and then figurative. Many things have gone from literal to figurative, some with both terms being slang, others with both terms not being slang, and yet others with just one slang.

It's also not clear that a computer bug was once something literal.

Is bug slang?

So, is a computer bug a slang word?

The Oxford English Dictionary says it is. Their sense 3 of bug, n.2 is "In various slang uses", and 3.b is "A defect or fault in a machine, plan, or the like". Their first example is from 1889, and it's been used in a software context since 1943 (three year's before Hopper's moth, a literal bug, in 1947).

So it's over 125 old, and has been used in computing about as long as there's been computers.

Define slang

It also depends how you define slang. Here's Oxford Dictionaries' definition:

A type of language consisting of words and phrases that are regarded as very informal, are more common in speech than writing, and are typically restricted to a particular context or group of people.

  1. Is "bug" regarded as very informal? Perhaps not very informal, but yes, I'd say it's at least informal.

  2. A good test for informality is the next test: is it more common in speech than writing? Generally, yes. In writing issue and defect are generally preferred.

  3. Is it typically restricted to a particular context or group of people? Yes, computer programmers and users, and in a computing (software) context.

  • In computer science, it is hardly possible to refer to dictionaries today, dictionaries are very slow in following the trends. In software engineering, however in official docs a bug encompasses a an array of various technical terms dealing with errors, faults, wrong engineering, etc. 'Bug' is too general a word to be a technical term.
    – Oleksii
    Commented Apr 15, 2015 at 12:20
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    This is a better answer than mine because it focuses on the OP's actual questions. With regard to #3, though, I think that the phrase "[there are] still a few bugs in the system" continues (in the United States at least) to be used outside computing as an expression generally applicable to situations where a design or process needs improvement. It occurs in one of the earliest Doonesbury cartoons from the early 1970s, for example, in connection with the dormitory roommate assignment system at Yale, when that system matches B.D. (a football player) with Michael Doonesbury (a nerd).
    – Sven Yargs
    Commented Apr 16, 2015 at 17:51
  • In a professional software development context I've seen "bug" used frequently in writing. This includes documents formal enough to eschew terms generally considered slang.
    – Jessa
    Commented Apr 17, 2015 at 20:27
  • If something is 'restricted' to 'computer programmers and users' is it really restricted, given that almost everybody nowadays uses computers? Most people these days have at least a vague understanding of what bug, in this sense, means, even if they don't use the word themselves.
    – jsw29
    Commented Jun 13, 2020 at 16:27

I would not consider "bug" to be a slang term primarily due to the fact that it has no unambiguous synonym, however I would consider it informal because of its etymology (real bugs getting stuck in vacuum tubes and causing computer errors). For example "defect" is ambiguous: Does it refer to a product or does it refer to a computer programming error?

Dictionary.com backs this opinion and has "bug" defined as 4. (Informal) a defect or imperfection as in a mechanical device, computer program or plan.

In short: "Bug" is informal but not slang.

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    I agree with you about the formality level of the term; however as my comments below the question, the other answer to this question, and the Oxford English dictionary make clear, the "bugs getting stuck in vacuum tubes" story cannot be the etymology of this meaning of "bug".
    – herisson
    Commented Apr 14, 2015 at 22:55
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    There is no way for a bug to get inside a vacuum tube (unless the vacuum tube has been previously smashed).
    – Hot Licks
    Commented Apr 15, 2015 at 0:42
  • Really? A term must have an unambiguous synonym to be considered slang? Can you link to anywhere else that gives a similar definition of slang?
    – Hugo
    Commented Apr 15, 2015 at 20:57
  • @Hugo That's not what I was saying. I was giving my opinion on why that single word shouldn't be considered slang.
    – Dog Lover
    Commented Apr 15, 2015 at 21:20

Generally speaking, the context in which a word is used determines its classification, rather than the word's history.

A "term" is a word with a specific meaning in a particular context (rather than general usage). "Slang" is informal communication.

"Bug" (referring to certain types of flaws) is technical terminology used by a group (programmers), making it jargon. As it's used in a particular context, it's a term. Jargon is often considered to be somewhat informal (as it's not well understood outside the group, you wouldn't use it in formal communications), putting it in the realm of slang.

In short, a word could be considered both a term and slang, regardless of its history or whether it's literal or figurative.

  • I'd say that the usage is far more widespread than merely among programmers. Computer Science is widely taught nowadays. Commented Jun 13, 2020 at 15:55

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