Than | then

Than and then sound similar in spoken English (especially in New Zealand English with the Kiwi habit of swallowing vowels) and so often get confused in written English.

Than

Than is only ever a comparison (apart from that very rare and historical usage mentioned by Ellen in the video - don't worry about that). Ellen did also explain that 'than' can be used to mean "instead of" when combined with "rather". What Ellen says is true, but we think that usage qualifies as (kind of) making a comparison.

A son should always grow to be taller than his mother.

Rather you than me

I would rather clean the oven than talk to him about it.

Examples from academic sentences:
What perpetrators fear is being caught, rather than being punished (Dupré, 2007, p. 195).

But a stronger bottom line than utility is needed for establishing a more structured and less corruptible moral foundation, especially in response to the problem of crime.

Reference:
Dupré, B. (2007). 50 philosophy ideas you really need to know. London, England: Quercus.

Then is a time reference: it is used to signal a point in time, or a sequence of some kind, or for signalling consequences.

♭♩ ...and then I go and spoil it all by saying something stupid like I love you ♪

It was easier back then, to disappear 'off grid' and live quietly away from what has now become invasive (but government-sanctioned) electronic surveillance.

Examples from academic sentences:

In the treble clef, the note immediately above this is named D, and D is followed by E, then F, and so on in sequence.

It would seem that a person's acknowledgment that moral character is worth something would be a prerequisite for then holding that person morally accountable.

Stephanie Paterik (2018) has shared this clever little trick (below) to help you remember them.

Reference:

Paterik, S. (2018, Nov. 7). When to use 'then' vs. 'than'. Howcast. Retrieved from https://www.howcast.com/videos/515768-when-to-use-then-vs-than-grammar-lessons