Learn Swedish: Allriskförsäkringen täcker varken självrisken eller den stulna bilen. - The all-risk insurance covers neither the deductible nor the stolen car.

In Swedish main clauses, varken ... eller (neither ... nor) acts as the sole negative marker. You do not add inte to the verb. Saying täcker inte varken is a common mistake for English speakers, but it violates Swedish grammar rules because varken already makes the sentence entirely negative.

Is självrisk the standard word for an insurance deductible?

Yes! It literally translates to self-risk. In Swedish insurance terminology, självrisken is the portion of the claim you must pay out of your own pocket before the insurance policy covers the rest.

Why does stulna end in an -a in den stulna bilen?

This is the Swedish double definite construction. When you have a definite noun like bilen modified by an adjective, you need the independent definite article den and the adjective must take its definite form, which ends in -a. Here, the past participle of stjäla (to steal) acts as the adjective, so stulen becomes stulna.

If I wanted to say the insurance covers either the deductible or the car, how would the structure change?

You would replace varken with antingen to get antingen ... eller (either ... or). Since antingen ... eller is not negative, the sentence would mean the insurance definitely covers one of those two things.