I've occasionally seen the abbreviations "O/P" and "I/P" used in a context where it can be inferred they mean "output" and "input" respectively. However, in years of doing electronics work (in the US) I've never actually encountered these particular abbreviations until recently on this site.

Example question: BJT Amplifier I/P O/P

Are these abbreviations common in other regions or languages? Should they be edited to conform to an English StackExchange site?

Note: the question has been edited, see history

  • 10
    \$\begingroup\$ Not to mention that "O/P" is more difficult to type than "output"... \$\endgroup\$
    – JYelton
    Apr 2, 2014 at 18:39
  • 5
    \$\begingroup\$ I personally don't like them. Is it really so much effort to strike 2 or 3 more keys to have a clear message that everybody understands? I think this is especially true for people that don't have English as their native language. On the other hand: Could I personally be bothered to edit a text only for this reason? Probably not. \$\endgroup\$
    – jippie
    Apr 2, 2014 at 18:59
  • \$\begingroup\$ @Jippie: Just downvote and look for some excuse to perhaps also close the question. \$\endgroup\$ Apr 2, 2014 at 19:38
  • 8
    \$\begingroup\$ @OlinLathrop I don't agree that a single unclear abbreviation is a reason for downvoting or closing a question. \$\endgroup\$
    – jippie
    Apr 2, 2014 at 19:51
  • \$\begingroup\$ @Jippie: A single abbreviation can be overlooked. But it sets the mood of the OP saving a few ms typing whether it makes the post annoying to read or not. That quickly dissipates good will and benefit of the doubt that might make the difference in downvoting and/or closing for other reasons. It's just not a smart thing to do. When you disrespect people, don't complain about the consequences. \$\endgroup\$ Apr 2, 2014 at 19:56
  • 7
    \$\begingroup\$ Don't vote with your blood pressure ;o) @OlinLathrop \$\endgroup\$
    – jippie
    Apr 3, 2014 at 5:06
  • \$\begingroup\$ JYelton, sorry but I took the freedom to edit both questions (yours and the linked one) \$\endgroup\$
    – clabacchio
    Apr 3, 2014 at 7:57
  • 1
    \$\begingroup\$ I've never seen this before either... Maybe it's a confusion of the more general abbreviation I/O? \$\endgroup\$ Apr 5, 2014 at 5:31
  • \$\begingroup\$ I've seen them before (UK) but think they're horrible. I/O is standard as Kurt says, but these are two words. Why is there a / in the middle of a word? In/Put?! Out/Put?! I wouldn't be surprised if the first use intended it to be an abbreviation for ~put/Port or similar. \$\endgroup\$
    – OJFord
    Apr 5, 2014 at 17:42
  • \$\begingroup\$ "But it sets the mood of the OP saving a few ms" <-- says the guy arguing against "O/P" and saving a few milliseconds. :-) FWIW, I agree it's ugly and annoying from fellow professionals. I think it better to hold back on inferring too much regarding writers whose backgrounds we don't necessarily know. \$\endgroup\$
    – gwideman
    Apr 5, 2014 at 23:14
  • 1
    \$\begingroup\$ With the large number of people here (including myself) that use OP for "original poster", O/P can just lead to a lot of confusion. \$\endgroup\$
    – tcrosley
    Apr 10, 2014 at 14:42
  • \$\begingroup\$ Definitely abbreviations are to be avoided if only a few extra keystrokes are needed to make the full word. I remember when I used "PSU" and nobody west of Ireland understood I meant power supply. Since then it made sense I don't use "PSU". i/p and o/p are definitely well used in the UK and I, for one (without trying to suck up) shall endeavour to remember this!! \$\endgroup\$
    – Andy aka
    Apr 12, 2014 at 20:23

7 Answers 7


No, these abbreviations and many others are NOT acceptable.

Only abbreviations that are very widly used and pretty much universal should be written here. This is a international list, so the readers will have lots of different conventions and personal contexts. Examples of acceptable abbreviations include TCP/IP, NPN, CMOS, FET, and even I/O pin.

Since a question is written once and read many times, it makes sense to further push the "work" of expanding abbreviations on the writer instead of the reader if there is any doubt. I have downvoted and sometimes skipped questions that were too annoying to read due to abbreviations. Sometimes I have left a comment, other times not. There is really no excuse for taking a few ms shortcut when writing at the expense of everyone reading, especially when the writer is asking for a favor from the readers.

The abbreviations you cite are far from common. I have never (yes, I'm certain about that) used either one myself, even when communicating with others in my geographic area, in over 30 years doing electrical engineering professionally. I personally find these particular abbreviations more annoying than most, just like w/o that I've sometimes seen stand for "without". I have to look at them and think about it, then mutter to myself something like "Why didn't that #*@^$$@ just say output in the first place?". There really is no excuse for this sloppiness and making everyone else do your work for you.

  • 2
    \$\begingroup\$ Regardless of the assumed intentions of the poster, I would agree that I/P and O/P are bad abbreviations and should be avoided. The 'slash' implies two different things that 'work together': Input/Output. Transmission Control Protocol/Internet Protocol. In/Put? What is put? \$\endgroup\$
    – dext0rb
    Apr 3, 2014 at 2:21
  • \$\begingroup\$ @dext0rb Isn't that just the way abbreviations are built in (American?) English? Like A/C for "air conditioning" or n/a for "not applicable"? \$\endgroup\$
    – AndreKR
    Apr 5, 2014 at 20:58
  • 1
    \$\begingroup\$ @AndreKR It is common to use slash for alternatives (like I/O for input OR output), or subsidiariness (as in TCP/IP, the TCP part of IP). In two-letter abbreviations of two words (n/a; a/c) slash indicates word break, and reinforces that it's an abbreviation. It may seem unnecessary, but is idiomatic for some abbrevs. Abbreviating a single word to two letters with a slash, as in b/c for because, or i/p for input, perhaps suggests the writer is ignorant of the fact this is a single word, or doesn't care. But it's up to the reader to decide what to infer and how offended to become. \$\endgroup\$
    – gwideman
    Apr 5, 2014 at 23:06
  • \$\begingroup\$ Oh, right... two words. \$\endgroup\$
    – AndreKR
    Apr 5, 2014 at 23:28

My 2 cents: if you find unnecessary abbreviations that are not immediately clear, edit/suggest an edit making them explicit and, as Passerby suggested, take the chance to improve other things. Our purpose here is not only to ask/answer questions, but also to help the existing ones to become awesome!

As always, if the edit is trivial and the post is old then it may be discouraged, but then a more substantial edit can help a lot.

EDIT: I would also add that non-common abbrevations can affect the reachability by search engines, so it might actually be negative.


A.C.R.O.N.Y.M.: Abbreviated Code Rarely Or Never Yielding Meaning.

That's actually in the Navy's Acronym Handbook. Or whatever the hell they called that thing.

The whole point of lampooning the thing in the manual was to point out the need for completely standardized communication. Granted, that was a military application, but I have found professionally that the lessons there apply almost universally. How many times have we all seen someone order WAY too many pieces of something because they thought one unit meant another? The difference between box and case can get you in really quite a lot of trouble.

I'm the new guy here, but I'm for enforcing standardized communication, if ever so gently. There should probably be a simple list of standard abbreviations that are accepted, and it should probably be put together by the big chief mucky-mucks on the site. Then it could be used as a learning tool by little guys like myself, to increase our exposure to things unfamiliar and help us generate better content.


I can't tell you whether they are "acceptable", as I don't have the time to read the entire Help section of any given Stack Exchange before I start asking questions. For example, is it a PCB or a PWB? I'm not sure what the convention is for this particular forum, so I'll just use PCB, and hope/pray I'm not in violation of the rules.

However, while I myself have never used these, the abbreviations are not unheard of. A quick google search turns up a site dedicated to acronyms, and the very first expansion for I/P is input http://acronyms.thefreedictionary.com/I%2FP, and the very first expansion for O/P is output http://acronyms.thefreedictionary.com/O%2FP.

Odd acronyms like that certainly do inhibit my ability to read a question or answer. But, personally, I would just move on if it bothered me that much. Most people who are posting these odd acronyms are newbies who simply don't know any better. Perhaps they had a professor or colleague who used I/P, and they picked up the habit, not knowing that it's an uncommon abbreviation (I had a professor who referred to block diagrams as "chunky monkey"). So a new user innocently asks a question in a manner that isn't exactly as prescribed, and they come back to their question looking for help, only to be punished with down votes or a closed question - all over something that they did not intentionally do? That seems unreasonably harsh to me.

Now, if a specific user is told by a moderator "hey try to use approved or common abbreviations, uncommon abbreviations make it more difficult to understand you", and then that specific user ignores the advice of the moderators and continues, that's downvote and close worthy. That behavior is intentional, and intentional misbehavior deserves down votes.

  • \$\begingroup\$ To be clear, my question is not about downvoting or closing. It's about whether to edit such abbreviations for standardization of site contents. \$\endgroup\$
    – JYelton
    Apr 2, 2014 at 22:11
  • \$\begingroup\$ My first concern was how common those abbreviations are, hence why I bring up the acronym web site first. My second concern was remedy. I should have been more clear - my first approach would be "warn to avoid uncommon abbreviations, and request the user edit their own post", second approach would be "ignore them". But the comment thread to your question, and the only other answer at the time, suggest downvote/close as remedy, not edit. I wanted to highlight how I view such an approach to be counter-productive, and would not even recommend it as a third approach except as punishment. \$\endgroup\$
    – ajs410
    Apr 2, 2014 at 22:18
  • 1
    \$\begingroup\$ Who defines what's common or worse, approved? \$\endgroup\$
    – Passerby
    Apr 3, 2014 at 0:46

When you publish academically, you clearly define the abbreviation on first use, and then you use it freely. If you only use it once, there's no need to abbreviate it. If you use a non-standard abbreviation, your peer referees will likely ask you to change it. If you use something really non-standard, it will probably be changed before proof by the page editor to match a style sheet.

Speaking of Style Sheets, IEEE has one, and it has a section on abbreviations.

Acronyms and abbreviations can be used to save time and space in the document. If the draft makes extensive use of acronyms or abbreviations, a subclause within the definitions clause entitled “Acronyms and abbreviations” may be provided. The acronyms and abbreviations subclause is not meant to take the place of the definitions clause. If acronyms and abbreviations are included in the definitions clause, Clause 3 should be titled “Definitions, acronyms, and abbreviations” and 3.1 and 3.2 titled “Definitions” and “Acronyms and abbreviations,” respectively.

Within text, the acronym or abbreviation should follow the first use of the full term (the first time in the introduction, then the first time in the body of the document, and then the first time in any annexes in which the acronym appears). The abbreviation or acronym should be placed in parentheses when following the full term.

Acronyms and abbreviations, followed by the full term only, should be listed in alphanumeric order. For an example of an acronyms and abbreviations subclause, see the sample draft in Annex B.

Exceptions to the convention listed above are approved SI units. SI unit symbols are not abbreviations and shall not be included in a list of abbreviations and acronyms. The treatment of letter symbols for units (e.g., mm for millimeter), letter symbols for quantities (e.g., R for resistance), and mathematical symbols (e.g., log for logarithm) is covered in IEEE Std 260.1 and IEEE Std 280 (see also Clause 14).

Acronyms and abbreviations should be avoided in titles of standards. However, if such use is warranted, the procedure stated above should be followed.

Personally, I get the O/P I/P thing, but its usually a "what does that mean?" process to get it figured out, and I'd eventually arrive at the right answer -- I guess I need some basic contextual reading lessons (I suppose I can use that as an excuse to turn down reviewing grants when the NIH asks me to). If I were to edit the example question, I would probably define it (i.e., "output (O/P)" ) if it were used more than once; I would probably replace it with the complete word if it were used only once; and I would probably remove it from the title (where there isn't much context).


A title where 3 out of 4 words are acronyms is not a good title.

When the acronyms are used properly, they don't impede (sometimes even improve) the flow of reading. When they are used improperly, they impede the flow of reading.

Abbreviations I/P (input), O/P (output), s/w (software), h/w (hardware), f/w (firmware), b/w (between), w/ and w/o (with and without). These are very handy for taking hand-written notes, especially in real time. But in the typed text, they should be used judiciously.

P.S. Here's another acronym question: What are acceptable abbreviations/shorthand for microcontroller?


Not uncommon, I have seen it used before, and if you can't understand O/P and I/P in context, then you need some basic contextual reading lessons. If you feel so strongly about it, just edit it and move on, but keep in mind, Try to make the post substantively better when you edit, not just change a single character. Tiny, trivial edits are discouraged.


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