The Korean particle -은/는 is perhaps the first particle any Korean language learner learns. It is known mostly as the topic particle and it is perhaps one of the most difficult to understand particle Korean grammar has to offer. Yet the basics of this particle are not overly difficult to understand.
The first and most important use of the Korean particle -은/는 is to mark the topic of the conversation/sentence. It marks what you want to talk about or what you want to explain. It is, of course, because of this use that this particle is known as the topic particle in Korean grammar.
가: 안녕하십니까. 저는 마크입니다.
나: 안년하십니까, 마크 씨.
A: Hello, I’m Mark
B: Hello, Mr Mark.
Another use for -은/는 is a follow up on the ‘new information’ use of the particle -이/가. After you introduced the new information, you use -은/는 with that ‘old’ information when you repeat it once more. This is to indicate you are still talking about the same thing as mentioned earlier during the conversation.
KR: 엣날에 한 할머니가 살았다. 할머니는 남편과 자식이 없었지만 검은색 고양이 두 마리가 있었다.
EN: One day an old lady lived. Grandma had no husband and children, but she had two black cats.
The last way you can use the particle -은/는 is when you compare two things to each other. In this case, however, -은/는 cannot only be attached to the subject, but you can also attach it to the object or location, etc. Keep in mind that save for the particles -을/를 and -이/가, all other particles, like -에, -에서, etc., remain so you will attach -은/는 behind them.
가: 사과가 있어요?
나: 아니요, 배는 있어요.
A: Do you have apples?
B: No, but we have pears.
How To Use
The topic particle -은/는 is not difficult to use as it follows the same general principles as the other frequently used particles, like -이/가 and -을/를. The Korean grammar principle it follows is the ‘batchim/no batchim’. If the noun ends in a batchim (consonant), you use the form -은. However, it ends in a no batchim (vowel), you use -는. After that, you are done with it.
Keep in mind that while the topic often is also the subject, this is not always true. Sometimes the topic is a different part of a sentence. This, however, is something you only start getting used to after a bit of practice and a lot of reading.