Choosing the right conjunction is important to make the meaning clear.

  • He is intelligent but hardworking.
  • He is intelligent and hardworking.

(Since the conjunction and connect similar ideas, it should be used in the above sentence.)

  • I have always been weak in mathematics and I have never failed a test.
  • I have always been weak in mathematics, but I have never failed a test.
(But is more appropriately used because the two sentences above have opposite ideas.)

 

When ‘and’ is used to connect two words or phrases in a sentence, no comma is used. Commas are used when there are three or more items in a sentence.

  • I had bacon and an egg.
  • I had bacon, a toast, and an egg.
 

Some conjunctions with accompanying words can be at the beginning or the end of a sentence.

  • I have a glass of milk before I go to bed.
  • Before I go to bed, I have a glass of milk.
(A comma is used when a conjunction introducing a subordinate clause comes before the main clause.)

 

We can start a sentence with a conjunction, or place it in the middle of a sentence.

  • If he is not here soon, we shall leave without him.
  • We shall leave without him if he is not here soon.
  • When you see him, please talk to him about it.
  • Please talk to him about it when you see him
  • Although she is my colleague, we hardly talk to each other.
  • We hardly talk to each other although she is my colleague.
  • Because the weather is bad, we decide not to go out.
  • We decide not to go out because the weather is bad.
  • Before she left, she cooked for them.
  • She cooked for them before she left.
  • After the accident, he decided to give up his job.
  • He decided to give up his job after the accident.
(As can be seen from the above sentences, we insert a comma when we begin a sentence with a conjunction.)