Easy-to-notice differences
Let's talk about some differences that are very easy to notice. First, English is written using the Alphabet while Korean is written in its own writing system, 한글 [Hangeul]. Second, while you have to put a space between two words in English (with the exception of shortened forms where an apostrophe is used, such as I'm, it's, we've, etc.), two or more words can be put together without space depending on the interactive functions of the words.
Less obvious, but more important differences
You don't have to be already good at speaking Korean in order to understand these differences. If you are just beginning to learn the language, just keep these tips in mind for when you want to learn more Korean in the future, or at least for the next time you help your students with their English composition.
1. Verbs over nouns - "I want to drink water a lot."
Nouns are equally as important as verbs in Korean, too. The same concepts that are expressed in English through adjectives and nouns, however, are often expressed through adverbs and verbs in Korean. For example, when you talk about drinking water, the basic structure is the same in both languages. Water is the object and drinking is the action. But when you want to make the sentence a bit more complicated, you start to see some differences.
Let us suppose you want to say "I want to drink a lot of water." In this sentence, "a lot of" or "much" is the part that modifies "water". You want to drink "much water". But in natural, everyday Korean, you say this in a different structure - "I want to drink water" + "a lot."
When you say 저는 물을 많이 마시고 싶어요. [jeo-neun mu-reul ma-ni ma-si-go si-peo-yo.], you mean that you want to do "the action of drinking water" a lot. The word that is being modified by "a lot" is not the noun (= water) but the verb (= to drink).
How about another example? Suppose you want to say "You have beautiful eyes." to someone. (Good luck!) In this sentence, you are talking about "eyes" that are beautiful - "beautiful eyes." But in Korean, most people would say "눈이 예쁘시네요." [nu-ni ye-ppeu-si-ne-yo.] Literally translated, it means "(Your) Eyes are beautiful." So the concept of "having" beautiful eyes disappears as you translate the phrase to Korean, and the "eyes" are now the subject of the verb "to be beautiful." When you want to score more points by saying "You have really beautiful eyes," you have to attach the word 정말 [jeong-mal] (= really) to the verb "to be beautiful (예쁘다)," not to the adjective "beautiful."
So look at this from a Korean student's point-of-view now. When they want to say "I, friends are many." in Korean, they have to say "I have many friends." in English. ("Wow, I HAVE them? They BELONG to me?") When someone says to them in English "You are a good singer," their reaction might be "What? I am not a singer. Maybe you mean that I sing well?"
So look at this from a Korean student's point-of-view now. When they want to say "I, friends are many." in Korean, they have to say "I have many friends." in English. ("Wow, I HAVE them? They BELONG to me?") When someone says to them in English "You are a good singer," their reaction might be "What? I am not a singer. Maybe you mean that I sing well?"
2. "Wait until the sentence is finished."
Here is another interesting feature of the Korean language: The main verb almost always comes at the very end of the sentence. So you usually need to wait until a sentence is finished in order to figure out whether it is a negative or a positive sentence, or to know which tense (past, present, future, present progressive, etc.) the whole sentence is in.
In English, you can say just the first few words, like "I don't think he …" and the other person instantly knows that your sentence is: (1) in the present tense and (2) a negative sentence. But in Korean, the "I don't think" part is expressed at the very end (i.e., "I + [all the details] + think + not." or "[all the details] + seem + not.") so you can't really know what the other person is eventually going to say if you don't listen all the way to the end.
Of course, native Korean speakers would often drop the end of their sentences or not speak very clearly toward the end, but that is when the key point can be easily delivered even with just the first few words. So in most cases, unless you can make some assumptions in advance from the context and the situation, you need to wait until a sentence is finished before you can figure out what the entire sentence is actually saying. For this reason, there is even a Korean saying that goes "한국말은 끝까지 들어 봐야 안다." [han-guk-ma-reun kkeut-kka-ji deu-reo bwa-ya an-da.]; which means, "When someone talks in Korean, you need to wait until the end of the sentence to really know what he means."
Normally when Korean people say something in Korean, they can start a sentence and still have some time before they think of which verb to use and which tense to make it. Therefore, when they need to say the same thing in English, they suddenly feel some burden from having to already have the verb ready at the beginning of a sentence. This "burden" and the universal shyness found in most beginner-level learners of a foreign language combined, it makes it even harder for Korean people to speak English, before they get use to the opposite order of words and thinking in English in the first place.
3. Guessing game
This is perhaps the most difficult part for both Korean students learning English and people learning Korean: the guessing game. In Korean, if not absolutely necessary, some parts of a sentence can be easily omitted by the speaker and the other person will usually have no problem understanding it. Not sure what this means? Let me explain a little bit more in detail.
Korean has these very convenient elements that are called "particles." Some of them are used like the English prepositions, but some particles mark the object, subject or topic of the sentence, which is expressed through the order of words in English. These particles make Korean sentences more flexible because the various parts of a sentence don't always have to be in the same place. And because sentence order is more flexible in Korean, native Korean speakers often drop parts of a sentence when the meaning is clear even without them.
For example, in English, the sentence "I watched a movie yesterday." would not be complete without the word "I" because there would be no subject. In Korean, however, if it is very obvious who watched a movie yesterday, it is sufficient to just say "yesterday movie watched" (어제 영화 봤어요).
Let's look at some more examples. When a Korean person says "괜찮아요?" [gwaen-cha-na-yo?], there is no subject in this sentence, so you need to tell from the context whether the subject is "it" (Is it okay?), "you" (Are you okay?), "they" (Are they okay?), etc. When you hear a sentence like "몇 시에 만나요?" [myeot si-e man-na-yo?], it all depends on the context whether this sentence means "What time are we going to meet (each other)?", "What time are you going to go meet them?" or even "What time are they meeting?"
Now look at this from a Korean student's point-of-view. In Korean, you seldom have to make a lot of effort to make sure there are no elements missing in a sentence. But suddenly in English, you have to be careful not to drop "a" in front of singular objects, mention the subject before the verb, make sure the word order is logical, etc.
Understanding language differences can help you understand your students better
Knowing these differences won't instantly make your classes easier or more successful, but I hope understanding and remembering these basic differences in the two languages will help you better understand some of the difficulties that your students are having in learning English.
source: http://www.talk.go.kr/newtalk/NewsLetter/2011-06-24_html/www/sub-5/sub_2.html