(Positive, Comparative, and Superlative)
Equal = Jon is so vet soos Don (Jon is so fat like Don) Memorize the pattern.
Unequal + Jon is vetter as Don (as=than)
Ultimate ! Jon is die vetste! (English fatest, Afrikaans vetste)
So, what's the problem?
When things are equal (positive): In English, we use AS, e.g. I am as strong as you. In Afrikaans, we use AS when things are unqual, e.g. Ek is sterker as jy. When things are equal, memorize this: I am SO strong LIKE you. (like=soos)
When things are unequal (comparative): In English we say He is strong THAN me. So, the tendency is to want to say Hy is sterker DAN my. Here we have two problems. You can already guess that DAN is not correct. It should be AS. The second biggie is the word MY. Think of it this way. The full sentence should read: He is stronger than I am. All that is left is He is strong than I. Yup, in Afrikaans we compare two subject pronouns. HY IS STERKER AS EK.
When something is the ultimate (Superlative): Here are two caveats.
i) The letter transposition Eng: -est Afr: -ste
ii) Which words take MORE and which ones do not. This list does not map perfectly between Afrikaans and English. For example. Die interessantste boek is .... The most interesting book is ....
Please consult the vocabulary list: Degrees of Comparison.