The name for a subobject (subgroup) which is wiped out by activity
I recognize this inquiry is very easy, but also for the life of me, I can not remember what we call this point. Googling for this has actually supplied no aid.
Take into consideration an object $A$ and also a 2nd object $B$ (allow them be teams if you so pick). We desire to take into consideration and also activity of $A$ on $B$. In addition there is a subobject $C \hookrightarrow B$ (subgroup) which is wiped out by the activity of $A$, i.e. the constraint of the activity of $A$ on $B$ to $C$ sends out $C$ to the absolutely no object (the absolutely no in $B$ which represents the unimportant team).
I assumed it would certainly be the bit of the activity, yet this term is booked for another thing (specifically those things which deal with every little thing).
I assume that this need to be described as Torsion, and also specifically, in the rear of my mind, I maintain assuming it is called the $A$ - Torsion of $B$. Yet I am not exactly sure.
Does any person recognize what this has been called the past?