I see many times the words "conjugacy" and "conjugation", and I don't really get the difference between the two. Especially, when we take an element of a group and want to say that this has some property "up to conjugacy/tion", which one is better, and why?
closed as too localized by Simon Thomas, Steven Landsburg, Marc Palm, Dan Petersen, Andrés Caicedo May 16 '12 at 19:36This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question. 


To expand upon Gerhard's comment, I would add the following: In English, the acy suffix tends to denote the nounification of an adjective and the ation suffix tends to denote the nounification of a verb. Obviously, 'conjugate' can act as both an adjective and a verb e.g. '$x$ and $y$ are conjugate' or 'One may conjugate $x$ by some element to get $y$' Since these phrases are mathematically the same, there is thus no mathematical difference between '$x$ and $y$ are equal up to conjugacy' and '$x$ and $y$ are equal up to conjugation' 

