# Why does \mathbf work with minuscle letters but \mathcal does not?

If I type

\mathbf{e}


I see what I expect, but if I type

\mathcal{e}


the result is a symbol that is certainly not a calligraphic 'e'. Is this a misconfiguration on my part or is it purpose? In the latter case, what is the rationele?

• There are just no lower-case calligraphic letters in the standard packages. You are doing nothing wrong.
– user229669
Nov 28 '20 at 1:57
• This question is about \mathbb instead of \mathcal but the underlying issue is the same. Nov 28 '20 at 13:15

You must load a package which defines lowercase \mathcal letters. If you are allowed to use it, I recommend unicode-math.
If you need to use legacy fonts, there are a few that contain a lowercase \mathcal alphabet, such as newpxmath, and a few that contain lowercase \mathscr but not \mathcal, such as stix2.
It is also possible to load the script or calligraphic alphabets of many different packages, with scaling, through mathalpha, and this is the best way to load a different calligraphic math alphabet in legacy LaTeX.
With the default \mathcal{e}, LaTeX will look up the AsCII value of e in a symbol font and, since it does not contain an ℯ , give you mojibake.