\begin{definition}[Definition:Relative Pseudocomplement]
Let $(L, \wedge, \vee, \preceq)$ be a lattice.
Let $x, y \in L$.
Then the '''relative pseudocomplement''' of $x$ with respect to $y$ is the greatest element $z \in L$ such that $x \wedge z \preceq y$, if such an element exists.
The relative pseudocomplement of $x$ with respect to $y$ is denoted $x \to y$.
\end{definition}