What is 이다 in Korean and How to Use 이다?

이다 is a verb meaning ‘to be’ in English. It is attached directly to a noun, making it the predicate of the sentence. 이다 is used to express that the subject and predicate are the same thing.

The formal descriptive form of 이다 is 입니다，and its interrogative form is 입니까? The corresponding informal forms of 이다 are 예요/이에요 which are the same for both the descriptive and interrogative forms, with the interrogative form rising in intonation as it is pronounced: 예요?/이에요? When the preceding noun ends in a vowel, 예요 is used, and when the noun ends in a consonant, 이에요 is used.

The negative form of 이다 is 아니다, meaning ‘not to be’.

Formal Polite Style	Informal Polite Style	Informal Polite Style
	Nouns with End Consonant	Nouns with End Vowel
입니다	이에요	예요
사과입니다 책상입니다	책상이에요	사과예요

How to Use 이다 to Build Sentences?

Example 1:

A: 무엇입니까?  (=뭐 예요?)

B: 의자입니다. (=의자예요.)

A: What is this?

B: It’s a chair.

Example 2:

A: 한국 사람입니까？ (=한국 사람이에요?)

B: 네, 한국 사람입니다. (=한국 사람이에요.)

A: Is she Korean?

B; Yes, she is Korean.