English Grammar: Than v. That
A common problem we see in our English classes, especially for speakers of Latin languages like Spanish or French, is confusion between than or that. In Latin languages, they are usually the same word, like que in Spanish, but in English we split them into two words for two ideas.
Than is always used for comparing two things. You cannot substitute that for than in a comparative sentence.
It is better that I thought. This is a common mistake. The correct sentence is: It is better than I thought.
That is a relative clause used to connect and add more information.
She took the test that was hard. Which test did she take? The hard test.
That is also a demonstrative pronoun. It replaces the object in the sentence.
Rock climbing is hard. Yes, that was hard. In this sentence that replaces rock climbing.
That is also a subordinating conjunction. It is used when connecting a two-clause sentence.
It is better that we go. The first clause is we go; the second clause or result clause is: It is better. In this case you can also use if, but if gives the sentence a different meaning because it is a conditional and means that we aren’t 100 percent sure the results of the clause.
Finally, that can also be used as an adverb.
Example: The test wasn’t that bad.
Ok, so that should answer most of your questions about that v. than. Let us know if you have more!