Ratio of the systemic exposure from extravascular (ev) exposure to that following intravenous (iv) exposure as described by the equation: \[F=\frac{A_{\rm{ev}}\ D_{\rm{iv}}}{B_{\rm{iv}}\ D_{\rm{ev}}}\] where \(F\) is the bioavailabilty, \(A\) and \(B\) are areas under the (plasma) concentration-time curve following extravascular and intravenous administration, respectively, and \(D_{\rm{ev}}\) and \(D_{\rm{iv}}\) are the administered extravascular and intravenous doses.