I'm trying to remake this fancy theorem/definition/lemma environnment, but I've got no any where to begin. Is it a known package or rather a homemade redesign?

Fancy definition environment

  • There is a package that produces that, well, not so brilliant output, but I’ll keep the secret. 😗😜
    – egreg
    Oct 21, 2019 at 19:37
  • Ah that's a bummer (but if you have better ideas for package, I'm all ear out)
    – Bast
    Oct 21, 2019 at 20:22
  • Have a look at the 'tcolorbox' package Oct 22, 2019 at 4:12

1 Answer 1


Check out the thmbox package, the manual contains several examples, but for completeness I have included a MWE.




  Let $M$ be a martingale, then $(\phi(M_t))_{t \geq 0}$ is a
  sub-martingale for all convex functions $\phi$ such that $\phi(M_t)$
  is integrable for all $t$.

  This follows from Jensen's inequality for conditional expectations,
  see any standard text book on this subject.


enter image description here

Do note that the proof is environment is also redefined. There are two additional styles L and S. The package is rather old and might have problems concerning page breaks. So as the comments suggest, implementing the style in another package might be a better solution—this answer implements the M style in the powerful tcolorbox package.


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