Than or Then

The English words than and then look and sound a lot alike, but they are completely different. If this distinction is harder than it should be, read this lesson and then try again.
 
Than
Than is a conjunction used in comparisons:

Tom is smarter than Bill.
This is more important than you might think.
Is she taller than you?
Yes, she is taller than I.

Technically, you should use the subject pronoun after than (e.g., I), as opposed to the object pronoun (me). However, English speakers commonly use the object pronoun.
 
Then
Then has numerous meanings.
1. At that point in time

I wasn't ready then.
Will you be home at noon? I'll call you then.

2. Next, afterward

I went to the store, and then to the bank
Do your homework and then go to bed

3. In addition, also, on top of that

He told me he was leaving, and then that I owed him money
It cost $5,000, and then there's tax too

4. In that case, therefore (often with "if")

If you want to go, then you'll have to finish your homework.
I'm hungry!
Then you should eat.

Exercises: http://www.towson.edu/ows/exercisethen2.htm
Exercises: http://www.towson.edu/ows/exercisethen5.htm


From:  http://www.elearnenglishlanguage.com/difficulties/thanthen.html