-이다

Usage notes

• The declarative ending 다 (-da) changes to 라 (-ra) in some environments; see 라 (-ra) for details.
• In the informal polite form, 해요체 (haeyoche), after vowels 이다 (-ida) is often pronounced as 에요 (-eyo) instead of 예요 (-yeyo) in many environments.
• 이다 (-ida) is the Korean positive copula. Along with its negative, 아니다 (anida), it is sometimes categorized as an adjective, but more 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.
• For the existential meaning of "be", see 있다 (itda).

Conjugation

• The chart below is for consonant-final nouns.
• After a vowel-final noun, the initial vowel 이 (-i-) is deleted when followed by a syllable beginning with a single consonant (야 (-ya) included), except in quite formal language:

  돌이다 / 바다다 ― dor-i-da / bada-da ― it's a stone / it's the sea

  돌이야 / 바다야 ― dor-i-ya / bada-ya ― it's a stone / it's the sea

  적이겠다 / 친구겠다 ― jeog-i-get-da / chin'gu-get-da ― he's probably an enemy / he's probably a friend

• It is not normally deleted when followed by a consonant cluster, except in quite colloquial language:

  나무입니다 / 나뭅니다 ― namu-i-mnida / namu-mnida ― it is a tree / it is a tree (colloquial)

• It is not deleted when used as a noun or adnominal.

  나무인 / 나무임 ― namu-i-n / namu-i-m ― which is a tree / it being a tree

Alternative forms

• 다 (-da) — after vowels
• 이더 (-ideo), 더 (-deo) — after consonants

See also