Conjunctions - But, Although

그러나 [But]

그러나 can only be used between sentences.

Book = 책
Banana = 바나나
read = 읽다
want to read = 읽고 싶다
wanted to read = 읽고 싶었다 (Verbs - Want)
sleep = 자다 slept = 잤다
like = 좋다 (plain)
like = 좋아한다 (present) (Verbs - Present/Past)

Eg. 

• 책을 읽고 싶었다. 그러나 잤다. [I wanted to read a book. But I slept.]
  
• 바나나는 맛있다. 그러나 나는 좋아하지 않는다. [Banana is delicious. But I don't like it]

The two sentences are linked by 그러나 but they are still separate.


~데/~지만 [But, Although]

To link two or more sentences into one sentence, ~데 or ~지만 are used.

● For verbs, add 데 to Verbs - Descriptive I
● For adjectives, add 데 to Adjectives - Descriptive

Eg.

• 쓰는 → 쓰는데 = write but / although I write
  
• 글씨는 쓰는데, 읽을 수 없다 = I write words but I cannot read / Although I write, I cannot read

• 사는 → 사는데 = live but / although it lives
  
• 물에서는 사는데, 땅에서는 못 산다 = It lives in the water but it cannot live on the ground / Although it lives in the water, it cannot live on the ground

• 어려운 → 어려운데 = difficult but / although it's difficult
  
• 외국어는 배우기 어려운데 재미있다 = A foreign language is difficult to learn but it's interesting / Although a foreign language is difficult to learn, it's interesting.

● For verbs and adjectives, add 지만 to a plain form without 다.

Eg. 

• 쓰다 → 쓰지만 = write but / although I write
  
• 글씨는 쓰지만, 읽을 수 없다 = I write words but I cannot read

• 살다 → 살지만 = live but / although it lives
  
• 물에서는 살지만, 땅에서는 못 산다 = It lives in the water but it cannot live on the ground

• 어렵다 → 어렵지만 = difficult but / although it's difficult
  
• 외국어는 배우기 어렵지만 재미있다 = A foreign language is difficult to learn but it's interesting.