Learn Croatian: Jesi li umoran?

In Croatian, you cannot start a sentence with a short verb form like si. When making a yes/no question that starts with the verb to be, you must use the full (emphatic) form. For you (singular), that full form is jesi.

What does the word li do in this sentence?

li is a question particle. To build a yes/no question, you take the full form of the verb (like Jesi), put li immediately after it, and then add the rest of the sentence. Together, Jesi li basically translates to Are you...?

If I want to ask a woman if she is tired, does the word umoran change?

Yes! Adjectives in Croatian must match the gender of the person you are describing. umoran is the masculine form. If you are asking a woman, you must use the feminine form umorna. The question becomes: Jesi li umorna?

How would I answer yes to this question?

In Croatian, it is very common to answer a yes/no question by repeating the verb. To say yes, I am, you use the full form of the verb for I, which is jesam. You can just say Jesam, or you can say Da, jesam.