This is the 154th most frequent Bulgarian word.
защо
"Why"
In this sentence, "защо" is used to inquire about the reason or motivation for studying Bulgarian.
Защо учиш български език?
Why are you studying the Bulgarian language?
In this example, "защо" serves to introduce a clause that specifies the aspect of difficulty being questioned.
Не разбирам защо е толкова трудно.
I don’t understand why it’s so hard.
Here, "защо" is part of a subordinate clause, introducing the reason or explanation for an action.