-이다

From Middle Korean -이다〮 (Yale: -ì-tá), from Old Korean 是 (*i-).

• (SK Standard/Seoul) IPA^(key): [ida̠]
• Phonetic hangul: [이다]

이다 • (-ida) (infinitive 여 or 이어, sequential 이니)

1. to be; the Korean copula.

   Antonym: 아니다 (anida)

   사람은 동물이다. ― Saram-eun dongmur-ida. ― Humans are animals.

   이 나무는 큰 편이다. ― I namu-neun keun pyeon-ida. ― This tree is on the big side.

   전쟁은 바람직하지 않은 일이다. ― Jeonjaeng-'eun baramjik-haji aneun ir-ida. ― War is undesirable business.

   악마도 한때 천사였다. ― Angma-do hanttae cheonsa-yeotda. ― The Devil was too once an angel.

• 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.
• See 있다 (itda) for the existential "be".

• 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 / chingu-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