How should I pronounce the following things? (These are complexities of algorithms.)

  • O(n)
  • O(n*log(n))
  • O(n^2)
  • 1
    This question is more appropriate for math.stackexchange.com or cstheory.stackexchange.com.
    – Mitch
    Commented Jun 1, 2011 at 16:28
  • 2
    @Mitch cstheory is for research level questions only, see cstheory.stackexchange.com/faq
    – Christi
    Commented Jun 2, 2011 at 18:25
  • I think this is a pointless question. Does OP really want to know whether O is pronounced as Owe rather than Big Oh? Or maybe it should be pronounced zer-OWE? I'm voting to close, and if I could delete it I would do that. Commented Jun 23, 2011 at 3:06

5 Answers 5


Pronunciation would be:

  • order n
  • order n log n
  • order n squared
  • 7
    If the context (of computational order) is already established, I've also heard "o of n" (etc). Commented Jun 1, 2011 at 16:38
  • 1
    Its just known as the 'Big O' in my discrete math class. aka the maximum amount of times an algorithm will be run. Commented Jun 23, 2011 at 2:56

In the talks I've seen that involve algorithm complexity, I've heard it most often pronounced "oh of n", "oh of n log n", etc.

Mathematicians and CS theorists also use a lowercase o and a capital ϴ for similar measurements with slightly different implications. In this case O( n ) would be pronounced "big oh of n", o( n ) "little oh of n", and ϴ(n) "theta of n".

  • A footnote on the Wikipedia article says O(g(n)) is pronounced "big-oh of g of n" or sometimes just "oh of g of n", referencing Cormen, Thomas H.; Leiserson, Charles E.; Rivest, Ronald L. (2009). Introduction to Algorithms (3rd ed.). Cambridge/MA: MIT Press. p. 47.
    – Stuart F
    Commented Aug 24, 2022 at 12:01
  • @StuartF: Thanks for adding the reference! Commented Aug 24, 2022 at 13:42

That is commonly referred to as Big O Notation, and since my days as a math/CS student I have always pronounced it (and heard it pronounced) as "Big O of n", "Big O of n log n", etc.


I think it's also common to just say "oh" followed by whatever is inside the parentheses.


There is an "oh n log n" algorithm for that problem

Doesn't that require "oh n squared" time in the worst case?


The ‚Θ -notation asymptotically bounds a function from above and below. When we have only an asymptotic upper bound, we use O-notation. For a given function g(n), we denote by O(g(n)) (pronounced “big-oh of g of n” or sometimes just “oh of g of n”) the set of functions

O(g(n)) = { f(n): there exist positive constants c and n0 such that 0 ≤ f(n) ≤ c.g(n) for all n ≥ n0}

ref: Introduction to Algorithms, fourth edition

  • This was probably unneeded. It does not tell us anything new about the question ("pronunciation"); and furthermore it has been more than 10 years.
    – GEdgar
    Commented Aug 24, 2022 at 10:11

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