Learn Finnish: Lammas on usein vuohta puhtaampi. - The sheep is often cleaner than the goat.

This is the partitive comparative structure you are learning right now! Instead of saying kuin vuohi (than a goat), we can drop the word kuin (than) and put the thing being compared to into the partitive case (vuohta).

Could I say Lammas on usein puhtaampi kuin vuohi instead?

Yes, absolutely. Both mean exactly the same thing. The version with kuin is slightly more common in everyday spoken Finnish, while the partitive structure (vuohta puhtaampi) is very common in written Finnish and sounds a bit more concise.

Why does vuohta come before the adjective puhtaampi?

When you use the partitive case to mean 'than', the word in the partitive almost always comes directly before the comparative adjective. If you used kuin instead, it would come after: puhtaampi kuin vuohi.

How do we form the comparative puhtaampi from the basic adjective puhdas (clean)?