Main Difference – Then vs Than
Although the two words than and then sound and look alike, they have vastly different meanings and functions. The main difference between then and than is that than is a conjunction whereas then is an adverb. In spite of this difference, than and then are also two of the most confusing words in English.

Then – Meaning and Usage
Then is an adverb which indicates time and consequence. It can be used to indicate three basic meanings.

Then – At that time

He didn’t know the truth then; he thought they were trying to help him.

Food products were way too costly then; people were starving.

He was recruited to the Special Task Force by the then president.

It was only then that I realized that I was at the wrong place.

By then, everybody was exhausted.

Then – Afterwards, next

I made dinner, and then my friends called me out for dinner.

I’ll drink my tea and then eat these biscuits.

He won the first race; then he won the second race.

He said that he had gone out for a drink with friends and then returned home.

Then – in that case, therefore

If he gives you the money, then you’ll have no worries.

If you do as he says, there’ll be no problem then.

As long as you don’t break the law then it’s OK with me.