At one point (Let/427), Tolkien stated that the plural form Belain (and presumably its singular Balan) did not exist in Sindarin and its derivative Orbelain “Vala-day” was a phonetic translation of Q. Valanya. Elsewhere, though, Balan is well attested as a Sindarin word.
balannoun. Vala, divine power, divinity
pl1. Belain** ** n. Vala.
tûr (i dûr, o thûr, construct tur) (victory, mastery, control; master, victor, lord), pl. tuir (i thuir), coll. pl. túrath.
1) Rodon (pl. Rodyn, coll. pl. Rodonnath), 2) Balan (i Valan), pl. Belain (i Melain). In ”Noldorin”, the pl. form used with the article was "iMbelain" (LR:365 s.v. KIRIK).