When I first joined this site, I had to figure out “OP” from context. Finding out what “CW” means was much easier, as it is often spelled out in full. CFV I had to be point-blank told about. It seems that there ought to be an obvious and easily-accessible place of explanation for all acronyms used on this site and, for that matter, all the jargon used on this site, for things like “closed”, “dis-accepted”, and even for seemingly obvious things like “up-vote”, “down-vote”, and perhaps a candid list of hidden gottchas, like the silent no-warning 5-minute timeout on editing a comment.

It seems like it wouldn’t take much to have a drop-down list available on both main and meta, the text in the box being something like “click here for an explanation of ACRONYMS and jargon used on this site”. This drop-down box could be in the right-most column where currently tangential stuff (like questions from other sites) is currently displayed.

WDYT? (What do you think?)

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    $\begingroup$ Mia ekrano glaciiĝis kiam mi klakis sur ĝi. $\endgroup$
    – Mike Jones
    Commented Sep 28, 2011 at 9:06
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    $\begingroup$ Mi estas vere mizera aŭdi tion sed mi ne scias kion fari pri ĝi. $\endgroup$
    – Did
    Commented Sep 28, 2011 at 12:45
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    $\begingroup$ @Didier, CFV = call for votes, apparently. $\endgroup$
    – Dan Moore
    Commented Sep 29, 2011 at 19:23
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    $\begingroup$ As I've learned from Willie Wong's answer here, meta.SO has Stack Exchange Glossary - Dictionary of Commonly-Used Terms, which contains some acronyms, too. $\endgroup$ Commented Jan 9, 2013 at 11:34
  • $\begingroup$ @MikeJones: translation for those of us just beginning our Esperanto studies? $\endgroup$
    – Ron Gordon
    Commented May 15, 2013 at 14:46
  • $\begingroup$ This question is related to the points raised in meta.math.stackexchange.com/questions/12202 $\endgroup$
    – Mark S.
    Commented Dec 29, 2013 at 17:12

3 Answers 3


A community wiki post is in order, methinks. Actually, the meaning of most of these terms can be found by Searching the Fantastic Web, but here are some of them for your convenience:

AFAICT - as far as I can tell
AFAIK - as far as I know
AKA - also known as
BTW - by the way
bump - doing something (e.g. editing) to a post so that it rises to the top of the list of posts
CFD - call for discussion
CFV - call for votes
close - make a question no longer open for answers to be added
CV - Cross Validated, the StackExchange site for statistics
CW - community wiki, like this post.
DV - downvote
EoQS - Enforcement of Quality Standards
FAQ - frequently asked questions
FGITW - fastest gun in the west
FWIW - for what(ever) it's worth
GIYF - Google is your friend
help vampire - those who suck the life and energy out of generously helpful people by expecting others to do their work for them
HNQ - hot network question
HTH - hope this helps
HW - homework
IANA$\ast$ - I am not a(n) $\ast$, where $\ast$ is most often lawyer but on math.SE might be more often "algebraic geometer", "number theorist", "logician", etc.
iff - if and only if
IIRC - if I recall/remember correctly
IM((V)H)O - in my ((very) humble) opinion
IOW - in other words
ISO - in search of
LHF - low hanging fruit, questions that are (relatively) easy to answer
LHS - left hand side
LMGTFY - Let me google that for you
main - (when used on Math SE) refers to the main Math SE site
meta - (when used on Math SE) refers to the meta site for Math SE
MO - MathOverflow, the research level uncle of MSE. Which brings us to...
MSE - Math Stack Exchange (also sometimes referred to as MathSE, m.SE, M.SE, or math.SE) or Meta Stack Exchange the meta-site for the entire Stack Exchange network (also known as meta.SE).
MSO - Meta Stack Overflow (also meta.SO), the discussion site associated with SO; which was used for SE network-wide discussions, bugs and feature requests before new Meta Stack Exchange was started.
NARQ - not a real question; mostly used in connection with voting to close a question
not an answer - not an answer to the stated question; typically used for very interesting content that is too long for a comment
NSC - necessary and sufficient condition(s)
NSFW - not safe for work
OP - original post(er); whichever of the two meanings is intended is usually inferable from context.
OTOH - on the other hand
ping - notify using the @-notification system in comments
PSQ - Problem Statement Question (also here), aka Please-Solve Question, a question whose body contains only the statement of a problem ("Prove that ..." or "Please Solve ...")
reopen - make a closed question once again open for answers to be added
RHS - right hand side
QED - Quod Erat Demonstrandum, Latin for "which was to be demonstrated". Used to end a proof
SE - Stack Exchange, the network of Q&A sites including this one. Sometimes used as *.SE to denote a particular site of this network (e.g. physics.SE, stats.SE)
SEDE - Stack Exchange Data Explorer
SO - Stack Overflow, the oldest and largest site of the SE network
s.t. - such that / subject to
TFAE - The Following Are Equivalent.
TLA - Three Letter Abbreviation
tl;dr - Too long; didn't read. Sometimes a dismissal; occasionally denotes a brief summary of a verbose post.
vote - that is, upvote/downvote; the clicking of the arrows on the left of posts to show interest/agreement, or the opposite.
WLOG - Without Loss Of Generality
WRT - With respect to (used generally for differentiation and integration)
WTS - want to show
YMMV - your mileage may vary (I don't know how well this will work for you)
+1/-1 - explicit indication that you upvoted or downvoted a post; indicates agreement/disagreement
∎ or $\square$ (square box, tombstone) - sometimes used in place of QED, q.v.
♦ identifies a moderator of the site

Everybody else: add to this post as you see fit.

  • $\begingroup$ A half loaf is better than none, so I have up-voted and accepted your answer. $\endgroup$
    – Mike Jones
    Commented Sep 25, 2011 at 3:34
  • $\begingroup$ I'm still inviting other people to edit this, to make a more-or-less usable dictionary. $\endgroup$ Commented Sep 25, 2011 at 4:06
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    $\begingroup$ I've never seen OP used to refer to a post, only to a poster. Also, I've always assumed +1/-1 is used to indicate "I have upvoted/downvoted this, because...", followed by a reason for the agreement/disagreement. $\endgroup$
    – user856
    Commented Sep 25, 2011 at 6:22
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    $\begingroup$ Like Rahul, I had never thought that OP could refer to the original post. But I like that interpretation. From this point on let's agree that when we criticize the OP, we are criticizing the post, not the poster. Makes for a friendlier site. $\endgroup$ Commented Sep 25, 2011 at 6:30
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    $\begingroup$ I had always thought of "+1" as an idiom. @Rahul's interpretation works for me, too. :) $\endgroup$ Commented Sep 25, 2011 at 6:41
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    $\begingroup$ @Rah In OP the O denotes original / opening and the P denotes poster / post. The latter (post) denotation is in use, e.g. see the Wikipedia Internet forum page. $\endgroup$ Commented Sep 25, 2011 at 16:26
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    $\begingroup$ And how about "lorem ipsum" as "nonsense text used for, among other things, satisfying a minimum character count"? $\endgroup$
    – Mike Jones
    Commented Sep 28, 2011 at 9:08
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    $\begingroup$ Oh @Gerry, you're such a kidder. :D Morally, I'd alphabetize, but it might break the joke... $\endgroup$ Commented Oct 4, 2011 at 13:05
  • $\begingroup$ Do we have to have the common ones, like btw, too? It makes the list more cluttered. $\endgroup$
    – user1729
    Commented Jan 9, 2013 at 13:14
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    $\begingroup$ I would have gone to my grave thinking IANA meant "Internet Assigned Numbers Authority" only if it weren't for this post. $\endgroup$ Commented May 14, 2013 at 20:23
  • $\begingroup$ @GEdgar, see my comment to Gerry. $\endgroup$ Commented May 15, 2013 at 14:27
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    $\begingroup$ "QED" could also stand for "Quite Easily Done" :) $\endgroup$ Commented May 23, 2013 at 1:13
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    $\begingroup$ An example of correct usage: "IMO, IMO can be on MO." $\endgroup$
    – Ziyuan
    Commented Jun 9, 2013 at 21:24
  • $\begingroup$ Looks as if in an SE (= Stock Exchange) $\endgroup$
    – Ziyuan
    Commented Jun 9, 2013 at 21:29
  • $\begingroup$ Is there any "fastest gun in the west" problem discussion here in MSE meta? $\endgroup$
    – Shuhao Cao
    Commented Jun 19, 2013 at 22:07

Mathematical abbreviations:

This is not intended to be an enumeration of mathematical notation that happens to consist of capital letters, such as $\Bbb Z, SO(3),$ or $GF(8)$, but only commonly-appearing acronyms for specific English phrases. Nor is it intended to be an exhaustive catalog of every abbreviation ever used. It should contain only the most commonly-used abbreviations.

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    $\begingroup$ It would be great if users tried to use acronyms sparingly and tried to spell them out at least once, especially when dealing with beginners. While REF or SVD may seem like perfectly obvious and common acronyms, it is very hard for a non-native speaker and non-expert to guess their meanings, especially if they are just starting out in linear algebra and had virtually no exposure to the technical terms in English. You might gain a few seconds by using the acronyms but 100 readers will lose a few minutes by deciphering them. $\endgroup$
    – Martin
    Commented May 15, 2013 at 19:29
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    $\begingroup$ I agree with Martin. I'm not trying to recommend that any of these be used. Rather, I'm trying to document the abbreviations that are used, as an aid to people who don't recognize them. $\endgroup$
    – MJD
    Commented May 15, 2013 at 19:46
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    $\begingroup$ I also agree with Martin. I think the best way to help with understanding of acronyms is to try never to use them without first explaining them. Most parts of mathematics are largely acronym-free, and I think this is commendable. Conversely, I found it weird when all of a sudden multiple posts appeared on meta concerning "PSQ", as though it were obvious to all what that was supposed to be. (Even after learning what P, S and Q stood for, the intended meaning was still not completely clear to me!) $\endgroup$ Commented May 15, 2013 at 23:24
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    $\begingroup$ Second order logic? In some communities, SOL is "Sod Out of Luck." $\endgroup$ Commented May 16, 2013 at 11:02
  • $\begingroup$ Wikipedia has a huge list here (but it is missing e.g. BMO!) $\endgroup$ Commented Jul 4, 2021 at 11:53

Here is the link to the similar list at the English Stack Exchange site:


See it to find out what TPTB means:)


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