Từ nối although: mặc dù
Although it was rain heavily, they went to school
Từ nối because: bởi vì
He had good grade because he studied hard

1.And :và
-Dùng bổ sung, thêm nghĩa vào 1 thứ khác.
* She is a beautiful and smart girl.

2. Or: hoặc, hay
- Dùng chỉ lựa chọn
*Hurry up, or you will be !
  You have to choose one: white or black?

3.Because/As/Since: bởi vì
- Dùng để bổ sung nguyên nhân hoặc lí do:
a)Because:
C1:Because + MĐ1 ,MĐ2.
*Because I was lazy,  failed my exam.
C2:MĐ2, because + MĐ1.
* I failed my exam because I was lazy.
b)As/Since:
(Thường đứng đầu câu )
*As he was sick, he couldn't take part in the competition.
  Since my dog was dirty, I took him to the petshop.
{MĐ1 : nguyên nhân,lí do/ MĐ2: kết quả,điều kiện}

4.So :vì vậy, vì thế, nên
-Bổ sung kết quả cho câu
- Đứng trc mệnh đề2 ( chỉ kết quả), đứng ở giữa câu và sau giấu phẩy.Ko đứng đầu câu.
MĐ1+,so+ MĐ2  = Because MĐ1, MĐ2.
* I had a tootache, so i couldn't eat anything.   
= Because I had tootache, i couldn't eat anything.

5.But : nhưng
 - Dùng kết nối 2 MĐ ngược nhau trái ý nhau.
-Thường đứng giữa câu, sau dấu phẩy( phải có liên kết)
 * He works very hard, but he earns a little money.
    Her house is small but her garden is large.