Of native Korean origin.
- To be (something); to equal
Usage notes 
이다 (ida) is the Korean positive copula. Along with its negative, 아니다 (anida), it is often categorized as a Korean adjective, but often placed in their own grammatical category distinct from both verbs and adjectives. Some grammars classify 이다 (ida) as a particle and, like a particle, it is appended to the preceding word without an intervening space.
Some inflections of 이다 (ida) have both a -이에- form and a -예- form. For those inflections, the former is used when the preceding word end in a consonant, the latter when the preceding word ends in a vowel. Likewise for the inflections that have both a -이었- and -였- form.
- 해라체 (haerache, “plain”): -이다, -이었다 or -였다, -이겠다; -이냐, -이었느냐, -이겠느냐
- 해요체 (haeyoche, “polite”): -이에요 or -예요/-에요, -이었어요 or -였어요, -이겠어요
- 해체 (haeche, “informal”): -이야 or 야, -이었어 or -였어, -이겠어
- 합쇼체 (hapsyoche, “formal”): -입니다, -이었습니다 or -였습니다, -이겠습니다; -입니까, -이었습니까 or -였습니까, -이겠습니까