Korean Grammar by TOPIK Level

이다 is the Korean copula, the equivalent of 'to be' in English, and it attaches only to nouns. Its negative is 아니다. The polite forms are 이에요 (after a consonant) and 예요 (after a vowel); the formal forms are 입니다/아닙니다.

있다 expresses existence or possession ('to have', 'to be somewhere'), and 없다 is its negative ('not to have', 'not to be there'). The polite forms are 있어요/없어요. When speaking about someone you respect, use 계시다/계세요.

이에요/예요 is the polite (해요체) form of 이다, the verb 'to be', and it is what you use in everyday conversation. The rule: 이에요 after a syllable ending in a consonant, 예요 after one ending in a vowel.

아/어/여요 is the polite (해요체) ending for verbs and adjectives in everyday conversation. Which one you take follows vowel harmony: if the last vowel of the stem is ㅏ or ㅗ → 아요; any other vowel → 어요; and 하다 verbs → 해요.

았/었어요 is the polite past-tense ending. The rule: if the last vowel of the stem is ㅏ or ㅗ → 았어요; any other vowel → 었어요; and 하다 verbs → 했어요.

-(으)ㄹ 거예요 is the most common way of expressing the future or an intention in everyday Korean. It means 'will...', 'I plan to...', or it can be a guess. It comes from -(으)ㄹ 것 + 이에요, contracted to 거예요.

Korean has three main ways of forming a negative: (1) 안 before the verb or adjective (the short negative, a matter of will), (2) -지 않다 attached to the stem (the long negative, more formal), and (3) 못 before the verb (cannot, for lack of ability).

-(으)세요 is the polite, honorific way of giving a command or making a request - 'please do...' - used with elders, strangers and customers. It is a contraction of 하시어요.

-고 싶다 expresses the wish to do something, the equivalent of 'want to...'. It attaches only to verbs, never to adjectives. First and second person take -고 싶다; the third person takes -고 싶어하다.

-고 is a connecting ending that lists actions or qualities, either simultaneous or one after another - 'and' or 'and then'. The stem before -고 is not marked for tense; only the final verb carries it.

-아서/어서 joins two clauses to give cause and effect ('because... so...') or one action followed by another ('... and then...'). The rule: ㅏ/ㅗ → 아서; other vowels → 어서; 하다 → 해서. Important: the past tense is NEVER used before -아서/어서.

-(으)러 가다/오다 gives the purpose of going or coming somewhere - 'to go in order to...' or 'to come in order to...'. It is used only with verbs of motion: 가다, 오다, 다니다.

-(으)ㄹ 수 있다 expresses ability or possibility - 'can'. Its negative, -(으)ㄹ 수 없다, means 'cannot'. The 수 here is a bound noun meaning 'way' or 'means'.

-에 있다/없다 states where a person or thing is, or is not. The particle -에 marks the location when it goes with 있다/없다.

-(으)면 expresses a condition ('if... then...') or a repeated situation ('whenever...'). A stem ending in a vowel or ㄹ takes 면; a stem ending in a consonant takes 으면.

-지만 joins two contrasting clauses - 'but' or 'although'. It attaches straight onto the verb or adjective stem, whether it ends in a vowel or a consonant.

-(으)니까 gives a reason as the speaker sees it. Unlike -아서/어서, it can be used with commands and suggestions, and it can carry the past tense.

-(으)려고 하다 expresses an intention or a plan to do something - 'to intend to', 'to be going to'. Unlike -고 싶다, which is a wish, this is a decision already made.

-아/어 보다 expresses trying something out, or having experienced it - 'to try -ing'. Vowel harmony applies: ㅏ/ㅗ → 아 보다; other vowels → 어 보다; 하다 → 해 보다.

-아/어야 하다 expresses obligation or necessity - 'must' or 'have to'. -아/어야 되다 means the same thing and is more common in speech.

-는 것 같다 expresses a guess or a tentative opinion - 'it seems that', 'apparently', 'I think that'. How it is conjugated depends on the word class and the tense.

-아/어 있다 expresses the state that continues after an action is completed. It is not the action in progress but the condition it leaves behind - unlike -고 있다, which is the action itself happening.

-(으)ㄴ/는데 is a versatile connecting ending: it supplies background, marks a mild contrast, or simply leads into what comes next. It is softer than -지만 and needs no clear opposition.

-거나 joins two verbs or adjectives with the sense of 'or', offering a choice between two actions or states. It is only for verbs and adjectives; with nouns you use (이)나.