and annarr-tveggi, adj. or used adverbially, [-tveggja is a gen. form, -tveggi a nom.], plur. (dual) aðrirtveggju, dat. plur. -jum; in other cases tveggja, tveggi are indecl.:—one of twain, either; annattveggja þeirra, Grág. i. 236; ok er annattveggja til, at vera hér, hinn er annarr, there is choice of two, either to stay here, or …, Fms. xi. 143, N. G. L. i. 117; ef annarrtveggi hefir haldit öðrum, Grág. i. 29: with gen., a. þeirra, either of them, 149: dual, either of two sides, en þá eru þeir skildir er aðrirtveggju eru lengra í burt komnir en ördrag, but then are they parted when either of the twain is come farther away than an arrow’s flight, of combatants on the battle-field, Grág. ii. 19: neut., annattveggja, used as adv.; annattveggja—eðr, either—or; a. vestna eðr batna, Clem. 50. The word is rare in old writers, and is now quite out of use; as adv. annaðhvort—eða, either—or, is used.