What is the correct pronunciation for the mathematical abbreviation 'cos' when it is not pronounced in its complete form 'cosine'? I pronounce it as 'k-aw-ss', but a couple of Canadian friends I have pronounce it as 'k-oh-s' (like the adjective 'close'). I tried looking up dictionaries but none that I came across list the IPA / phonetic pronunciation for the mathematical abbreviation.

(I think the former is the British English pronunciation, and the latter is the American English / Canadian English pronunciation.)

  • Another way of putting what my Canadian friends are pronouncing the term as would be 'cosine' with the 'ine' chopped off, as Stan Rogers mentioned in his answer below. Commented Mar 3, 2011 at 8:25
  • Another (possibly) interesting variation in pronunciation - for 'sinh' (hyperbolic sine, I pronounce it like 'shine' while my Canadian friends pronounce it like 'cinch'. And so on for other hyperbolic maths abbreviations. This one is documented in the OED. Commented Mar 3, 2011 at 8:37
  • I like cinch for sinh, and kosh for cosh. By the way, how do you pronounce tan? Tangent or tangens? In Russian, it is tangens.
    – timur
    Commented Mar 18, 2011 at 15:08
  • 1
    @timur In its abbreviated form, I pronounce tan just like that - as in 'sun tan'. Otherwise, I pronounce it as 'tangent'. Commented Mar 24, 2011 at 3:04
  • @Ankur What about tanh?
    – timur
    Commented Mar 24, 2011 at 13:11

4 Answers 4


In England everybody I know pronounces this so that it rhymes with "because".

  • This is what I found at my university (Surrey) too. Commented Mar 3, 2011 at 8:59
  • 3
    Or like Bill Cosby :)
    – Benjol
    Commented Mar 3, 2011 at 9:14
  • 4
    There are other slightly alien words where UK English naturalises an <o> to /ɒ/ (as in UK 'cot') but N.Am English prefers an /oʊ/ (as in 'coat'). Examples that occur to me are 'kudos' and other Greek words in '-os', but I'm sure there are others with a different final consonant.
    – Colin Fine
    Commented Mar 3, 2011 at 12:55
  • @Colin I think your comment comes quite close to the answer I was looking for; as in, the origin of the different pronunciations. Commented Mar 3, 2011 at 14:03
  • 2
    But how do you pronounce 'because'? The 'au' can be like the 'o' in 'pot' or the 'ou' in cousin or 'or' as in 'born', @tchrist They do to me!
    – Simd
    Commented Apr 1, 2015 at 12:48

In speaking, I'd never use either of those pronunciations. "cos" means "cosine" -- say "cosine". Therefore I'd pronounce it "co-sign" ;)

  • 2
    It's like asking how to pronounce "Mr". It's pronouced as the word it is, even if it is shortened. Commented Mar 3, 2011 at 23:35
  • 3
    'Mr' was originally the abbreviation for Magister or Master (rather like Dr). It's now its own word, with irregular pronunciation. Commented Jul 5, 2011 at 11:36
  • Yes, even when written "cos", pronounce "cosine".
    – GEdgar
    Commented Jul 11, 2011 at 13:50
  • 1
    @David: Yes. Although that is more likely to be pronounced as an abbreviation because 1. log is just a word, so an unambiguous pronunciation exists for it, and 2. it shortens 4 syllables to 1, whereas cosine to cos at most shortens 2 syllables to 1. Commented Feb 20, 2014 at 1:21
  • 1
    @David: And while we're at it yes, I would pronounce "ln" as "natural logarithm" Commented Feb 20, 2014 at 1:22

Well, I'm Canadian, and I was always taught (and taught, myself, when I was teaching) what would be rendered koʊs in the IPA (hard c, long o, hard s) -- exactly like "cosine" with the "ine" left off.

  • 7
    +1 American here, and I've only ever heard this version [koʊs, kəʊs].
    – Jon Purdy
    Commented Mar 3, 2011 at 8:24
  • Thanks -- I just noticed I missed pasting in the upside-down omega dealie (obviously, I have all of these glyphs on tap, but I can't get at them directly on this <expressive glyphs missing> machine -- it was configured for Chinese and Hebrew originally, and I haven't been able to exorcise all of the weirdness yet).
    – bye
    Commented Mar 3, 2011 at 8:38
  • I added a comment to the question on the difference in pronunciation of hyperbolic trig abbreviations. Maybe there's a similar difference for cos? Commented Mar 3, 2011 at 8:40

For what it's worth, my maths teacher says cos like coz with a 'z' sound at the end, as opposed to cosine which he says co, long o, sine as in sign (s-i-y-n).

N.B. tan is just as is sounds, with the 'a' short.

  • On those rare occasions when I needed to refer to hyperbolic functions, I would pronounce "sinh" as "sin-huh", "tanh" as "tan-huh" and "cosh" to rhyme with "posh" or "gosh". (The "-huh" would be more like blowing air out the nose than a pronounced word.) I would also refer to a natural logarithm as "linn"....and sometimes a factorial (e.g., n!) as "N", loud and emphasized. But these were all facetious; I would normally use the full names: hyperbolic [function], natural log[arithm], factorial, etc.
    – tautophile
    Commented May 28, 2018 at 15:43

Not the answer you're looking for? Browse other questions tagged or ask your own question.