proˈthetically,adv. [f.prec. + -ly2.] 1. (Cf.prec.) 1838Fraser's Mag. XVII. 167 The genuine poet works synthetically, or even in higher guise, prothetically, and never analytically. 2.Gram. By prothesis or prefixion. 1885Trans.Amer.Philol.Assoc. XVI. App. 33 Letters added prothetically.