In mathematics (particularly in abstract algebra), two mathematical structures are isomorphic when they are the same in some sense. More specifically, an isomorphism is a function between two structures that preserves the relationships between the parts. To indicate isomorphism between two structures \displaystyle{ \mathcal{A} } and \displaystyle{ \mathcal{B} }, one often writes \displaystyle{ \mathcal{A} \cong \mathcal{B} }.