I'm tired of it. I can't STAND it! There are 2 words, THEN and THAN. They're COMPLETELY different words.

At that time: I was still in school then. Come at noon; I'll be ready then.
Next in time, space, or order; immediately afterward: watched the late movie and then went to bed.
In addition; moreover; besides: It costs $20, and then there's the sales tax to pay.
Used after but to qualify or balance a preceding statement: The star was nervous, but then who isn't on the first night of a new play.
In that case; accordingly: If traffic is heavy, then allow extra time.
As a consequence; therefore: The case, then, is closed.

Used after a comparative adjective or adverb to introduce the second element or clause of an unequal comparison: She is a better athlete than I.
Used to introduce the second element after certain words indicating difference: He draws quite differently than she does.
When. Used especially after hardly and scarcely: I had scarcely walked in the door than the commotion started.

It seems so many people don't even realize the word THAN exists. They use THEN in both speech and text. Every time I hear people misuse 'then' I get a nearly uncontrolable urg to 'knock their block off'. If people only took the correct usage of these words away from english 101 and 102 I'd think the classes worth the time.