Same here english is not my native language. There are many other errors that makes me cringe, like people writing "could of". Most of them are done by people whose english is their primary language. But on the other hand I also see people doing similar errors in my mother tongue.

I remember an SAT question about "taking for granted". One of the other options was "taking for granite". I had never wondered about how this mostly-spoken phrase would be written out, or how the orthography would shed light on its meaning.

I was surprised to realize that a phrase I knew very well, I had probably never read (and definitely never written).

I'm a native english speaker and I can't tell you the difference between then and than. lol.

I'm sure there's a better example, but I've always explained it like so:

"than" is for comparisons; e.g. smaller _than_, older _than_

"then" is used to indicate timing; chew _then_ swallow, wash _then_ rinse

It's certainly an incomplete explanation, but if someone else can share an explanation that is more succinct and/or complete than my own, I'd be interested in seeing it.

That is exactly how we learned it too and I can't figure out why people don't use these correctly.

Another one for "than" is also if you can replace it with "instead of". "Rather than learning the language, he went to a football game". Not "Rather - then learning the language later - he went to a football game first". Well actually there 'then' is correct but I had to make a broken up sentence that you would never write but you might say it. If you want to tell someone about this, you start with 'rather' then think of explaining first that he did go learn afterwards so you interject your own sentence and then go on. But when writing you have enough time to form a proper sentence.

Of course auto correction can play a role nowadays. I wrote "of" more often recently and a typoed "ofg" might be corrected to "of" and not "off". Sure.

Now what I do understand is that native speakers actually forget the rules meaning the "why" something is correct. After a while you can usually just tell what's correct. It just "sounds right" and you can't explain it to someone else.

I appreciate this example. I don't know why these two words always stump me. I feel pretty capable grammatically, but my brain completely forgets to remember these examples.

I'll add these examples to my notes so I can write correct emails at least. lol

I can try:

I finished the job THEN my boss paid me. I finished the job AFTER WHICH my boss paid me.

I'd much prefer him paying me THAN not paying me. I'd much prefer if he paid me AS OPPOSED TO not paying me.

For my dialect at least they sound the same, so in my brain they are the same.

Maybe that's my problem. I'm from the Southeast US (rednecks) and we pronounce them both dth-i-n. It's hard for me to type out but it's a harder I sound as the vowel. We use the same vowel for PEN (It goes PIN) and the name Ben goes BIN like BIN laden.