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

Examples:

  • 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.)

 

 

Examples:

  • 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.

Examples:

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

 

 

We can start a sentence with a conjunction or place it in the middle of the sentence. A comma is used when a conjunction introducing a subordinate clause comes before the main clause as shown here. The subordinating conjunctions are in bold. 

Examples:

  • 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 office 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 I go to bed, I have a glass of milk.
  • I have a glass of milk before I go to bed.
  • After the accident, he decided to give up his job..
  • He decided to give up his job after the accident.
 
(We use a comma when a conjunction introducing a subordinate clause comes before the main clause.)