Breakdown of Dobro jutro, prijatelju. Kako si ti danas?
kako
how
biti
to be (sam, si, je)
ti
you (sg. informal)
danas
today
Questions & Answers about Dobro jutro, prijatelju. Kako si ti danas?
How do we know this sentence is informal, and how would I make it formal?
The words si (are) and ti (you) show that this is informal. To make it formal, like when speaking to an older person or a stranger, you would use ste and Vi instead: Kako ste Vi danas?
Since si already means "you are", do I need to include the word ti?
You don't have to! In Croatian, the verb form si already tells us you are talking to "you" (singular), so you could just ask Kako si danas? Adding ti here just puts a little extra emphasis on the person.
Why is the word for friend prijatelju instead of the dictionary word prijatelj?
When you are directly calling out to someone or addressing them by a title or name, the ending of the noun often changes. This is called the vocative case. For many masculine words like prijatelj, we add -u to the end when speaking directly to them.
Why do we say Dobro jutro and not Dobar jutro?
Adjectives have to match the gender of the noun they describe. The word for morning, jutro, is a neuter noun because it ends in -o. Therefore, the adjective for "good" takes its neuter form, dobro, instead of the masculine form dobar.