Archaic/literary sentence-final intention form, from 터 + 이다. Declares the speaker's firm intention (first person only). Found in older novels and period dramas; in modern speech use -(으)ㄹ 테야, -(으)ㄹ 거야, or -(으)ㄹ게.
Example: 내일 갈 테다 (I shall go tomorrow).
Still worth learning: the same 터 + 이다 base lives on in the extremely common modern patterns -(으)ㄹ 텐데 and -(으)ㄹ 테니까, and the -(으)ㄹ here is the same future/prospective modifier used across many other grammar patterns.
Form:
-ㄹ 테다-을 테다Related:
-(으)ㄹ 텐데, -(으)ㄹ 테니까