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Let $R$ be an arbitrary ring. Given two $R$-modules $A$ and $B$, we may denote the set of all $R$-homomorphisms from $A$ to $B$ by $\operatorname{Hom}_{R}(A,B)$. If in addition we know that $A$ and $B$ are isomorphic $R$-modules, is there a specific way to denote the set of all $R$-isomorphisms from $A$ to $B$?

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    @DavidWard Please consider summarizing the comments into an answer, so that it gets removed from the [unanswered tab](http://meta.math.stackexchange.com/q/3138/15416). If you do so, it is helpful to post it to [this chat room](http://chat.stackexchange.com/rooms/9141/the-crusade-of-answers) to make people aware of it, so that it gets an upvote. For further reading upon the issue of too many unanswered questions, see [here](http://meta.stackexchange.com/q/143113/199957), [here](http://meta.math.stackexchange.com/q/1148/15416) or [here](http://meta.math.stackexchange.com/a/9868/15416).2019-05-06

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There doesn't seem to be a universally accepted notation, but the two that are clearly understood are $\operatorname{Iso}_{R}(A,B)$ and $\operatorname{Isom}_{R}(A,B)$. The former is probably preferable.