Isn’t it something how one letter, in this case the a or the e, can completely change the meaning of a word?
We’ll tackle than first. Than is used after a comparative adjective or adverb to express inequality. For example, I can say, “She ran faster than I ran.” I am comparing the speed at which she ran with the speed at which I ran; and in this case, I have a comparative adverb--faster.
Using the comparative adjective, older, I can say, “This house is older than our house.” In this case, two houses are being compared, and one is older than the other (notice the than in this last sentence?).
Than is additionally used after other, or any similar word, to express a difference of kind, manner, or identity. Such an example is, “An issue other than that one.”
All other times you would use then to express a moment in time. The following are examples:
At a point in time
She then went to the grocery store.
The then president of the company.
Since then, she became afraid of spiders.
I packed my suitcase, and then waited for the taxi.
Finish your dinner, and then you may go outside to play.
I had to go to the bank, and then to pay my bills.
He kicked the ball, and then ran after it.
Consequently, in that case
If you want to buy a new dress, then you’ll have to save your money.
If you eat half the pizza, then there will not be enough for us.
Remember that than is used when comparing; any other time, you would use then. Simple!
I will gladly respond to email inquiries regarding grammar and punctuation issues. If you are having difficulty or just need clarification on a certain subject, please email me and I will do my best to cover the topic in a subsequent article.