Overview
The expression N+이다 is the Korean copula, directly translating to "to be" or "is/am/are" in English. It is a fundamental grammatical element used to state the identity or classification of a noun. Unlike verbs or adjectives, which describe actions or qualities, 이다 connects two nouns, asserting that the first noun is the second noun.
Usage
N+이다 is primarily used to form declarative sentences where you identify or classify the subject. The structure is typically [Noun 1] + [topic/subject marker] + [Noun 2] + 이다 (conjugated form).
- It asserts that Noun 1 is Noun 2. For example, "저는 학생입니다" (I am a student).
- It can also be used to describe the nature or category of something. For instance, "이것은 책이에요" (This is a book).
- 이다 always attaches directly to the noun it identifies or describes.
Conjugation Rules
The base form of the copula is 이다. Its conjugation varies depending on the politeness level and whether the preceding noun ends in a consonant or a vowel.
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Informal-Polite (해요체):
- If the noun ends in a consonant: Noun + 이에요 (e.g., 학생 + 이에요 → 학생이에요 - "It's a student")
- If the noun ends in a vowel: Noun + 예요 (e.g., 의사 + 예요 → 의사예요 - "It's a doctor")
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Formal-Polite (합니다체):
- For both consonant-ending and vowel-ending nouns: Noun + 입니다 (e.g., 학생 + 입니다 → 학생입니다 - "I am a student"; 의사 + 입니다 → 의사입니다 - "I am a doctor")
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Informal-Casual (해체):
- If the noun ends in a consonant: Noun + 이야 (e.g., 친구 + 이야 → 친구이야 - "It's a friend")
- If the noun ends in a vowel: Noun + 야 (e.g., 나 + 야 → 나야 - "It's me")
Knowledge Plus
- 이다 is unique in Korean grammar as it functions as a copula, distinct from regular verbs and adjectives. While it shares some conjugational patterns with adjectives (like attaching directly to a noun without an object marker), its core function is to equate nouns.
- It can also be used to form questions by changing the ending: 이에요?/예요? (informal-polite) or 입니까? (formal-polite).
- The negative form of 이다 is N + 이/가 아니다 (e.g., 학생이 아니에요 - "I am not a student"). This uses the verb 아니다 ("to not be") and requires the subject marker 이/가.
- Remember that 이다 always attaches directly to the noun, without any spaces.