Questions & Answers about Băiatul are o soră și un câine.
Why do we use are for "has" in this sentence?
Why does the sentence use o before sister but un before dog?
Where is the word for "the" in băiatul?
Is the verb a avea a regular verb?
No, it is quite irregular. You cannot easily guess its forms just by looking at the dictionary form a avea. You will need to memorize that "I have" is am, "you have" is ai, and "he/she has" is are.