A $0$-groupoid is a $0$-category in which every morphism is invertible.1
1That is, a set.
Here's a breakdown of the differences between each PDF style:
| Style | Class | Font | Theorem Environments |
|---|---|---|---|
| Style 1 | book |
Alegreya Sans | tcbthm |
| Style 2 | book |
Alegreya Sans | amsthm |
| Style 3 | book |
Arno* | amsthm |
| Style 4 | book |
Computer Modern | amsthm |
*To be replaced with Linus Romer's Elemaints when it is released.
A $0$-groupoid is a $0$-category in which every morphism is invertible.1
