When should I use 이/가 as a 'copular complement particle'?

Question

I've read that 이/가 can be used as a particle to mark the complement of the particle 이다, its negative counterpart 아니다, and the verb 되다.

I have seen examples with 아니다 :

나는 아이가 아닙니다 – I am not a child.

and 되다

노인이 되기 전에 나쁜 짓 해야돼요 - You should have fun (?) before you get old

However, I'm not sure that I've noticed it used with the copula (이다) itself.

Can 이/가 be used as a complement particle with 이다? Can it be used with any constructions other than 이다, 아니다, and 되다?

Answer 1

이/가 is used at the end of a noun to express that the noun it accompanies plays the role of the subject of the sentence.

That being said, 이/가 can be used with any verb or the verb-like form of any adjective, and that, naturally, includes 이다.

[Examples with 이다]

• 내가 이 수업의 선생님이다. (I am the teacher of this class.)
• 이것이 내가 어제 잃어버린 축구공이다. (This is the soccer ball I lost last night.)

[Examples with other verbs]

• 의사가 수술을 집도했다. (The doctor performed the surgery.)
• 내가 갔다. (I went.)

[Examples with verb-like forms of adjectives]

• 그것보다 이것이 더 맛있다. (This tastes better than that. / This is more delicious than that.)
• 맥주가 차갑다. (The beer is cold.)

이/가 and 은/는 can be quite confusing for foreigners and some Koreans, but that's a seperate issue.

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After reading your comments, I realized that I was confused as well. (Or, only I was.)

According to the dictionary, there are three usages of 이/가, and two of them are about using with nouns.

One is about marking the subject, and I already covered this. The other is about marking the complement.

• 나는 개구리가 되었다. (I became a frog.)

In this example, the frog is obviously not the subject, but it is the complement. 는 marked the subject 나(I).

You might ask: "If 이/가 can be used to mark both the subject and the complement, can they be used twice in a sentence?" Yes, they can.

• 올챙이가 개구리가 되었다. (The tadpole became a frog.)

If 이/가 is used twice in a sentence, the first one marks the subject and the last marks the complement.

As far as '이다' and '아니다' are concerned, I am not sure if it is about marking the subject or the complement. Personally I think it's about marking the subject, so I covered in my previous answer. Hope this helps.

Answer 2

Adding to Cheong's great answer, the particle 이/가, in short, can be used as subject particles for any adjectives or verbs, and must be used as object equivalent if the word means a verb, but sometimes act as an adjective.

For example: 되다, 아니다, 있다, 없다, 그립다(miss).

네가 그 아이가 아니다.

거기서 버스가 있다.

어머니가 그리웠냐?

In the 3 examples above, the noun is treated as objects in English, but 이/가 used instead.

For the verb 이다, 이/가 is never added to the object. (AT LEAST, I have seen none yet).