https://doi.org/10.1351/goldbook.B00611
For @[email protected], the tendency of a compound to act as @[email protected] (@[email protected]) acceptor. The basicity of a @[email protected] is normally expressed by the @[email protected] of the conjugate acid (see @[email protected]). For Lewis bases it relates to the @[email protected] constants of @[email protected] and @[email protected]