Learn Swedish: Han centrerar leran efterhand som drejskivan snurrar. - He centers the clay gradually as the potter's wheel spins.

While medan just means two things are happening at the same time, efterhand som emphasizes a gradual process or progression. Here, it highlights that centering the clay is a step-by-step process that develops as the wheel continues to spin.

Could we use allteftersom instead of efterhand som in this sentence?

Yes, they are mostly interchangeable when describing simultaneous ongoing changes. Han centrerar leran allteftersom drejskivan snurrar would mean the exact same thing, though efterhand som can sometimes feel slightly more focused on the gradual passage of time rather than a direct proportional cause and effect.

What are the parts of the compound word drejskivan?

It is built from the verb dreja, which specifically means to shape clay on a potter's wheel, and skivan, meaning the disc or board. Since it ends in -n, it is in the definite singular form, meaning the potter's wheel.

If we started the sentence with the efterhand som clause, how would the word order change?

It would become: Efterhand som drejskivan snurrar centrerar han leran. Because the entire subordinate clause acts as the first block of information, the main clause must use inverted word order to keep the main verb centrerar in the strict second position (the V2 rule).