1 efa
að, in old writers usually spelt with i, ifa; efa occurs in Nj. 207, Hkr. ii. 326, Sks. 153, Stj. 256, Fms. ii. 42, iii. 115, vi. 184, Al. 43, Grett. 110 A, Bs. ii. 169, etc.; in mod. usage always with e:—to doubt, with acc.; engi ifar þat, Fms. x. 319: the phrase, efa sik, to hesitate, Grett. l. c.; skulu þér eigi e. yðr (doubt), at …, Nj. 307: used as neut. to feel a doubt, ifi þér nokkut, at, Fms. v. 38, Hkr. l. c., 623. 33; ifa (efa) um e-t, to doubt about a thing, Hkr. i. 223, Grág. ii. 47, Fms. ii. 283, v. 37, vi. 184.
2 efa
2. reflex., efask (ifask) í e-u, to doubt or hesitate in a thing; í því má engi maðr ifask, at …, Sks. 272 B; ekki efumk ek í því, 153, Stj. l. c.; Freysteinn efaðisk í, hvárt …, F. was in doubt, whether…, Fms. iii. 115; þér efisk í um þeirra almátt, ii. 42: efask um e-t, to doubt about a thing, x. 392; hvárt ifisk ér um ok hræðisk, Niðrst. 2.
3 efa
β. absol. to doubt, hesitate, Str. 22; statt upp ok ifask alls ekki, Hom. 119.
4 efa
γ. with gen., efask e-s, to change one’s mind in a matter, Grág. i. 312, 313.