Let $f: A \to B$, $f$ is an [[Injective]] [[Function]] [[Biconditional|if]]: $\huge \forall x \in A , y \in B :\, f(x) = y \iff x \neq y $ In other wrods, $f$ is [[Injective]] if for any *distinct* $x_{1} , x_{2} \in X$, $f( x_{1}) \neq f( x_{2})$ $\huge \forall y \exists! y \: :f(x) = y $ >[!example] ![[../../00 Asset Bank/Pasted image 20250127101257.png|invert_Sepia]]