mod. fýsn, f. = fýsi, Fms. i. 117, xi. 244, Fs. 22. Magn. 468, Str. 66; frá þessa heims fýstum ok girndum. Stj. 148; rangar fýstir, Fms. v. 217, Stj. 149: in eccl. sense the Gr. ἐπιθυμία is sometimes rendered by fýsn (e. g. fýsn holdsins, f. augnanna, 1 John ii. 16; heimrinn og hans f., 17), though more freq. by girnd (lust): fýsn is used much like Germ. neigung = impulse, inclination: it occurs in a great many compds, as fróðleiks-fýsn, lestrar-f., lærdóms-f., náms-f., desire for knowledge, learning; andleg f., holdleg f., spiritual, carnal desire; kærleiks f.; mannlegar fýsnir, human affections.