Korean copula

In Korean, the copula -이다 behaves like a verb, and is understood to English speakers as a verb, but is actually a particle. Suffix the word with -이에요 if it ends in a consonant, and -예요 if it ends in a vowel.

It is fairly versatile and context-sensitive:

물이에요.

It is water.

물이에요?

Is this water?

물가 음료예요.

Water is a beverage.

학생이에요.

You are a student.

학생이에요?

Are you a student?

Inflection

Differences with English

Note -이다 is not a one-to-one translation of "be" or "is." Unlike "to be" in English, -이다 cannot be used with adjectives:

✗ 사과 맛있이에요.

apples are delicious

• Literally, "apple is delicious."

✓ 사과 맛있어요.

apples are delicious

• Literally, this is more like "apple is deliciousing."

-이다 can sometimes be used with locations, albeit with a slight difference in nuance:It seems that the -이다 form is more casual and less precise, but that's merely hypothesis; 있다 should be preferred, I think.

✓ 나는 집이에요.

"I am home."

✓ 나는 집에 있어요.

"I am at home."

• The suffix -에 is a location-marking particle.

Conjugation

Unlike most other particlesThe copula -이다 is used like a particle and behaves like a verb, but the exact classification is difficult. The usual translingual definition of a "particle" excludes anything that can be inflected [cite:@Particle2025], and anything that has meaning independently; but still it is often classified as a particle in Korean. , -이다 is conjugated as if it were a verb.An 이-irregular verb, to be precise.

학생이에요

"I am a student."

학생이었어요

"I was a student."

The copula -이다 can also be directly conjugated into the future tense, but doing so brings surprising connotations: conjugating -이다 directly to "-일 거예요" does not express a factual "will be," but rather a subjective or estimated "might be," or personal intent of the speaker.Per Wiktionary, -(으)ㄹ as used in future tense conjugations is a "verbal and adjectivial irrealis adnomial suffix." In grammar, inflection in the irrealis mood is nonfactual, contrasting the realis or declarative mood. Adnomial simply means "relating to or involving action on nouns." [cite:@vicky2022ida]

학생일 거예요

"I might be a student," "I'm thinking of becoming a student."

그 사람 지수의 남편일 거예요.

"That person might be Jisoo's husband."[cite:@vicky2022ida]

• Not necessarily in the future! It could mean "that person might become Jisoo's husband in the future," but it could also mean "I think that person might be Jisoo's husband."

To speak factually of something being something else in the future, the verb 되다 ("to become") must be used.[cite:@vicky2022ida@armstrongIdaGrammarYour2025]

학생이 될 거예요

"I will become a student."

그 사람은 지수의 남편이 될 거예요.

"That person will become Jisoo's husband."Note that -이 as used in 남편이 is not the subject-marking particle, but rather a homographic particle marking the grammatical complement of 되다 or 아니다. See the definition and usage notes on the Wiktionary article for further details, but understand you needn't have a deep understanding of the underlying grammar to correctly use -이 with 되다 and 아니다.