Buzz
Although the word than is supposed to rhyme with man, many of us unintentionally pronounce it the same as then. This confusion, coupled with the fact that then and than differ by just one letter, explains why people often struggle to decide which one to use correctly.
When to Use Then
If you’re referring to time, the right choice is probably then.
For instance:
First, I’ll take a nap, and after that, I’ll clean the kitchen.
As Merriam-Webster points out, many common time-related expressions also use then, such as since then, back then, and every now and then. This also applies to conditional sentences with if, like:
If I take a nap, then I’ll have the energy to clean the kitchen.
When to Use Than
Than, conversely, typically denotes a comparison: less than, more than, bigger than, rather than, other than, and so on. It might seem obvious to use than when it's directly following a comparative term, but it can be a bit trickier when there’s a phrase in between.
For instance:
Taking a nap is a higher priority than cleaning the kitchen.
I’d prefer to take a nap than clean the kitchen.
This gets particularly tricky when beginning a sentence with the phrase No sooner had or No sooner did. Although you're referring to time, since sooner is a comparative, the correct choice remains than.
For instance:
No sooner had I woken from my nap than my roommate messaged me to ask if I had cleaned the kitchen.
And if anyone ever points out a then-vs.-than error in your writing, you could always say it was a deliberate reference to Middle English. In the Middle Ages, the two words were frequently used interchangeably.
