Topic Particle - 은/는

은 and 는 are topic particles. They are attached to nouns, adverbs, other particles or endings. It shows the subject of the sentence or may be used to show "contrast" or "emphasis".

When the noun ends in a consonant, you will use "은".

When the noun ends in a vowel, you will use "는".

Here are two examples:-

1. 물 : 물 + 은 ---> 물은
2. 우유 : 우유 + 는 ---> 우유는

I'll now give you some example sentences, including their English translation:-

1. 냉면이 쌉니다. 불고기는 비쌉니다 --- Naeng-myun is cheap. However, Bulgogi is expensive.
2. 버스가 느립니다. 지하철은 빠릅니다 --- The bus is slow. However, the subway train is fast.
3. 여름이 덥습니다. 겨울은 춥습니다 --- It's hot in summer. However, it's cold in winter.

도

도 is a particle with the meaning of "also" and "too". It may be attached to the end of other particles as in "-에게도" and "-과도".

Here are two examples:-

1. 책이 있습니다 + 노트가 있습니다 ---> 책이 있습니다. 노트도 있습니다.
2. 사과를 먹습니다 + 수박을 먹습니다 ---> 사과를 먹습니다. 수박도 먹습니다.

Now i've shown you the way "도" works, i'll now give you some example sentences with their English translation, so you can fully see how it's used.

1. 예습을 합니다. 복습도 합니다 --- I prepare the lessons. I go over the lessons, too.
2. 책을 읽습니다. 신문도 읽습니다 --- I read a book. I read a newspaper, too.
3. 선생님을 만납니다. 친구도 만납니다 --- I meet a teacher. I meet a friend, too.
4. 영화가 재미있습니다. 소설책도 재미있습니다 --- The movie is interesting. The novel is interesting, too.

Object Particles - 을/를

을 and 를 are object particles which come after a noun and shows the "object" of the verb.

When the noun ends in a consonant, you will use "을".

When the noun ends in a vowel, you will use "를".

Here are two examples:-

1. 책 : 책 + 을 ---> 책을
2. 교과서 : 교과서 + 를 ---> 교과서를

In spoken language, it may be omitted or abbreviated into "-ㄹ" after a vowel.

Here's an example using the abbreviation:-

1. 영화를 보고 커피를 마셨어요 ---> "영활 보고 커필 마셨어요"

I'll now give you some example sentences, including their English translation:-

1. 신문을 봅니다 --- I read a newspaper.
2. 커피를 마십니다 --- I drink a cup of coffee.
3. 수영을 합니다 --- I swim
4. 지우개를 삽니다 --- I buy an eraser.

Subject Particle - 이/가

이 and 가 are subject particles. Particles which come after a noun and shows "subject" are: -께서, (에)께서, etc.

When the noun ends in a consonant, you will use "이".

When the noun ends in a vowel, you will use "가".

Here are two examples:-

1. 연필 : 연필 + 이 ---> 연필이
2. 딸기 : 딸기 + 가 ---> 딸기가

When "이" and "가" is attached at the end of "나, 너, 저, and 누구," the words change into:

1. 나 ---> 내가
2. 너 ---> 네가
3. 저 ---> 제가
4. 누구 ---> 누가

Here are some examples using the word change:-

1. 내가 가요
2. 네가 갔니?
3. 제가 가겠습니다
4. 누가 갑니까?

I'll now give you some example sentences, including their English translation:-

1. 연필이 있습니다 --- There is a pencil.
2. 안경이 없습니다 --- There is not a pair of glasses.
3. 시계가 비쌉니다 --- The watch is expensive.
4. 딸기가 맛있습니다 --- The strawberry is delicious.