Learn Swedish: Om han hittar sitt bygglov ska han fälla trädet på sin egendom. - If he finds his building permit, he will cut down the tree on his property.

Both sitt and sin are reflexive possessives, meaning they refer back to the subject of their own clause. In the first clause, han is the subject who finds his own permit. In the second clause, han is the subject cutting down a tree on his own property. If we used hans, it would mean he was dealing with some other man's permit and property!

Why does the sentence use sitt for the permit but sin for the property?

The reflexive possessive must match the gender of the thing being owned. Because bygglov (building permit) is an ett-word, we use sitt. Because egendom (property) is an en-word, we use sin.

Why is the word order ska han fälla instead of han ska fälla?

This is the V2 (verb-second) rule. The entire subordinate clause (Om han hittar sitt bygglov) counts as the first piece of information in the sentence. Therefore, the main verb (ska) must take the second position, pushing the subject (han) to the third position.

Why use the verb fälla instead of a general word for cut?