"The man falls down."
English words derive some of their meaning based on position relative to other words. If a word is switched around, the meaning of the sentence changes.
Mary killed John. ≠ John killed Mary.
Korean words have markers added instead. The general meaning can stay the same even when the word order changes. More importantly, since the verb is always at the end of the clause/sentence, the marker identifies what case the word is in, because if both the subject and object come before the verb, how does one tell if a single noun that comes before the verb is a subject or object?
메리가 죽였어.: Mary killed. (She initiated the action of killing.)
메리를 죽였어.: Mary was killed. (She received the action of killing.)
조니가 메리를 죽였어.: Johnny killed Mary. (She received the action of killing—which Johnny initiated.)
은/는 is the topic marker, 가/이 is the subject marker. It's a fairly unintuitive distinction for western speakers, but they are an important part of Korean grammar, so you'd do well to learn about it.
I'm not sure what the best resource is to learn it, but here's one:
From that post, I liked this sentence:
> One of the easy way is to remember topic marker emphasize more on the verb while subject marker emphasize more on the subject
I'm not the best authority on the subject (I'm learning too), but from what I understand, the subject marker is often replaced with a topic marker to signify that the subject of the sentence is the same that's been mentioned earlier in context and thus the verb is more important in the sentence.
Good luck and hopefully you can find a good explanation that works for you :)
(This is coming from someone who knows a little Japanese.) Subject markers tend to mean "It was Mary who..." and topic markers are more like "Speaking of Mary, [some topic that was related to Mary in some way]". The subject marker is more explicit in Mary's involvement in the verb.
A subject marker more clearly defines the subject. For example, "dogs" as a subject might imply "the dogs bit me" or "some dogs bit me" depending on context, but not "all dogs in general have bitten me". In contrast, a topic marker could very well be referring to dogs in general (unless "those" is explicitly stated)... depending on context.
Here is what I found out.
The original form of the verb "fall down" is 넘어지다.
We choose between 즙니다and ㅂ니다 (the latter with a contraction between the final syllable of the verb wihout the stem다) based on the final syllable structure of the verb without the stem다.
When the syllable is a closed one (with an ending consonant), we just get rid of the stem (다) and attaching 즙니다.
If the syllable is an open one (ending with a vowel), then we contract this syllable with ㅂ followed by니다 (i.e. choosing ㅂ니다). And this is what happens to 넘어지다 (fall down). First, we truncate the stem 다 and ger 넘어지, and secondly we put 넘어지 and ㅂ니다 together and merge the last syllable of the former with the first ofbthe latter. And voila, 넘어집니다.
너머지다 is the verb. Since the verb root (지) ends in a vowel, ㅂ니다 is added.
Verb roots that end in strong consonants get an intervening ㅅ added:
- 맵다 → 맵습니다
- 맞다 → 맞습니다
- 살다 → 삽니다 (ㄹ is a weak consonant with vowel-like qualities, so it is deleted and ㅂ니다 is appended as if the root ended in a vowel)