sole sufficient operator

A sole sufficient operator or a sole sufficient connective is an operator that is sufficient by itself to define all of the operators in a specified set of operators.

In logical contexts this refers to a logical operator that suffices to define all of the Boolean-valued functions, $f:X\to 𝔹$, where $X$ is an arbitrary set and where $𝔹$ is a generic 2-element set, typically $𝔹=\{0,1\}=\{\mathrm{false},\mathrm{true}\}$, in particular, to define all of the finitary Boolean functions, $f:{𝔹}^k\to 𝔹$.