Simple notation question O(2pi)

[s00mb]

What does it mean when you see an equation that has some terms then there is a O(λ) or O(π) in it? For example N(λ) = Cm Vol(M, g)λ m + O(λ m−1 ) . I self study and see this often but it is never explained in the books I use and it drives me nuts. Is this some sort of error function?

 

[mathman]

A =O(x) means A is of the same order of magnitude as x.

 

[fresh_42]

Here is it in detail:
https://en.wikipedia.org/wiki/Big_O_notation
... and down the side the related notations.

 

[s00mb]

Thanks again especially for the quick responses