A Quick and Simple Dictionary

adjunction

1. Noun.  The act of joining; the thing joined or added.
2. Noun.  (category theory) A form of similarity between a pair of categories $mathcal\{C\}$ and $mathcal\{D\}$ which is weaker than equivalence, which in turn is weaker than isomorphism. Given functors $F:mathcal\{C\}\; ightarrow\; mathcal\{D\}$ and $G:mathcal\{D\}\; ightarrow\; mathcal\{C\}$, ''F'' is "left adjoint" of ''G'', and ''G'' "right adjoint" of ''F'', denoted as $F\; dashv\; G$, if .