Questions & Answers about Ti imaš jedan kišobran, a on ima dva.
Why is a used here instead of i to mean and?
In Croatian, a is used to show a contrast between two things, similar to whereas or but in English. Because we are contrasting what you have with what he has, we use a instead of the regular word for and (i).
Why does this sentence include the pronouns ti and on? Doesn't Croatian usually drop them?
You are right that pronouns are usually dropped! However, when we are directly comparing or contrasting two different people (you versus him), we keep the pronouns to add emphasis.
Why is the number one written as jedan here?
If we were talking about a feminine object instead of an umbrella, would the word for two (dva) change?