이/가 vs 를/을

[bakaeigo]

This is something that has confused me for a while. How do I know when to use 이/가 and when to use 를/을? Also, why is it that when you say "남자 친구가 있숩니까?" , it has 가, but when you say "이거 있숩니까?" it has no 가 or 이?

Thanks in advance

[the_haunted_boy]

를/을 is usually used before verbs as an object marker.

[austinfd]

This is something that has confused me for a while. How do I know when to use 이/가 and when to use 를/을? Also, why is it that when you say "남자 친구가 있숩니까?" , it has 가, but when you say "이거 있숩니까?" it has no 가 or 이?

Thanks in advance

As the_haunted_boy said,

를/을 is a "particle" that attaches to the end of a noun to indicate that it is the OBJECT of the sentence:

나는 김치를 먹고 싶어요 (I want to eat kimchi)

이/가 is a particle that attaches to the end of a noun to identify it as a SUBJECT of the sentence:

자동차가 검은색이에요 (The car is black)

Also, why is it that when you say "남자 친구가 있숩니까?" , it has 가, but when you say "이거 있숩니까?" it has no 가 or 이?

Because often these particles are dropped from every day conversation. To be absolutely grammatically correct, you include them, and if you have a really picky teacher, they will make you use them. But in fact, it is almost always obvious in normal conversation, so in speaking they get dropped. The sentences you provided are both fine (some spelling mistakes) it's just that in one the subject marker got the ax.

남자친구가 있습니까?
이거 있습니까?

I don't know for sure, but since your question ends in the formal politeness level, it feels a little awkward to remove the subject marker. Speaking in that level resembles reading from a book, so I think that speech at level tends to include all the markers. In that case, your second sentence would probably be:

이것이 있씁니까?
(거 is a shortened form of 것 and since 것 ends withㅅ you use 이 and not 가)

[bakaeigo]

I'm afraid I'm still a little confused.
If 이/가 is the subject marker, then what's 는/은: for?

[javiskefka]

은/는 is the topic marker, and it can go in front of almost any word in the sentence, not just a noun or pronoun. It indicates what the focus or emphasis of the sentence is.

A few examples:

어제 제가 과일을 먹었습니다.
I ate some fruit yesterday.

어제 저는 과일을 먹었습니다.
I ate some fruit yesterday. (In comparison to what others ate)

어제 제가 과일은 먹었습니다.
I ate the fruit yesterday. (Some particular fruit known to the listener)

어제는 제가 과일을 먹었습니다.
Yesterday, I ate some fruit. (As opposed to what I normally eat)

You can also observe proper use of the subject and object particles above.

[bakaeigo]

I think I get it now.
Thank you!