Questions & Answers about Die Wüste ist viel größer als die Insel.
Why does größer have an umlaut when the basic word groß doesn't?
Many short, one-syllable adjectives with an a, o, or u get an umlaut when you add -er to compare things. So, groß (big) becomes größer (bigger). You will see this often with common adjectives like alt -> älter (older) or jung -> jünger (younger).
I often confuse als and wie when making comparisons. Why is it als here?
You use als (than) when there is a difference between the two things you are comparing, which is exactly what happens with -er words like größer (bigger than). You only use wie when two things are exactly the same size or degree, like in so groß wie (as big as).
Why do we use viel here instead of sehr?
Just like in English, you wouldn't say "very bigger"—you say "much bigger." In German, sehr means "very" and is used with normal adjectives (sehr groß). To make a comparative stronger, you must use viel (much), giving us viel größer.