Learn Swedish: Eftersom vi studerat företeelsen förstår vi problemet. - Since we have studied the phenomenon, we understand the problem.

It is built from the verb förete (to exhibit or appear) plus the abstract suffix -else, turning it into an en-word noun meaning 'phenomenon' or 'occurrence'. In this sentence, it has the definite suffix -n tacked onto the end to mean 'the phenomenon'.

Why is the verb studerat used here without har?

In Swedish subordinate clauses—like the one starting with eftersom here—it is grammatically correct and very common to drop the auxiliary verb har (or hade). You could just as easily say Eftersom vi har studerat, but dropping it is typical in formal or written Swedish.

Why does the second part of the sentence say förstår vi instead of vi förstår?

This is the classic V2 (verb-second) rule. The entire first clause (Eftersom vi studerat företeelsen) acts as the first piece of information in the overall sentence. To keep the main verb in the second position, förstår must come immediately after the comma, followed by its subject vi.

Could I start this sentence with därför att instead of eftersom?