Q:

Does a one-to-one function exhibit "injectiveness" or "injectivity"? 

I'm preparing some tutorials for students and I'm faced with writer's block.  If I want to say a function is injective/one-to-one, would the function demonstrate "injectivity" or "injectiveness"?  Similarly, what is the convention used for surjective/bijective functions? 

A:

Neither "injectivity" nor "injectiveness" have made it to the Oxford English Dictionary.   A MathSciNet search for titles containing "injectivity" yields 702 hits, but "injectiveness" just 7.   So I'd say "injectivity" is the clear winner.