nLab
Notation

In the following $C$ and $D$ are categories, $x$ and $y$ are objects…

• $1$ – See point
• $2$ - See interval category
• $\mathrm{Arr}(C)$ - See arrow category
• $C^{\to }$ - See arrow category
• $[C,D]$ - See functor category or enriched functor category or internal hom
• $D^C$ - See exponential object or functor category
• $C\downarrow D$ - See comma category
• $C/D$ - See comma category
• $(C,D)$ - See comma category
• $C\downarrow x$ - See over category a.k.a. slice category
• $C/x$ - See over category a.k.a. slice category
• $x\downarrow C$ - See under category a.k.a. coslice category
• $x/C$ - See under category a.k.a. coslice category
• $x\backslash C$ - See under category a.k.a. coslice category
• $C(x,y)$ - See hom-set or hom-object
• $\mathrm{hom}(x,y)$ - See internal hom or hom-set
• $\mathrm{Hom}(x,y)$ - See internal hom or hom-set

Discussion

Eric: Let’s list here a library of notation for the uninitiated (like me).

Toby: If you like, but what we really need to do, I think, is to explain notation right where it's used. So if you put a query box pointing out wherever notation is used that you don't understand, then that might help.

Eric: Sure, but sometimes I come across notation in a reference (not necessarily on the n-Lab) and it is not 100% clear from the context what concept that notation corresponds to. I thought this could be an index of notation that merely points to the correct page.

Toby: OK, fair enough.

Urs: yes, sounds good

category: meta