I’ve seen a lot of people using these words incorrectly. So how can you remember the difference? (Tip: take a close look at the letters in bold.)
‘Then’ means ‘next’ or ‘at that time‘. For example: We organised the meeting and then we started working on our new project. Everything was so much easier back then.
‘Than’ is used in a comparison. For example: The new office chairs are more expensive than the old ones. They are much nicer than the old ones.