diff --git a/2021_Algebra_I.tex b/2021_Algebra_I.tex
index a3331d3..6e0be69 100644
--- a/2021_Algebra_I.tex
+++ b/2021_Algebra_I.tex
@@ -2305,9 +2305,9 @@ If $P_e $ with $e < d$ was $\neq 0$, it could not be a multiple of $P$ contradic
 
     The bijectivity of the $\phi_{U, (U_i)_{i \in I}}$ is called the \vocab{sheaf axiom}. 
 \end{definition}
-\begin{dtrivial}
+\begin{trivial}+
     A presheaf is a contravariant functor $\mathcal{G} : \mathcal{O}(X) \to C$ where $\mathcal{O}(X)$ denotes the category of open subsets of $X$ with inclusions as morphisms and $C$ is the category of sets, rings or (abelian) groups.
-\end{dtrivial}
+\end{trivial}
 \begin{definition}
     A subsheaf $\mathcal{G}'$ is defined by subsets (resp. subrings or subgroups) $\mathcal{G}'(U) \subseteq \mathcal{G}(U)$ for all open $U \subseteq X$ such that the sheaf axioms still hold.
 \end{definition}