This is the 18th most frequent Estonian word.
mida
"What."
Here, 'mida' is used as an interrogative pronoun to ask about an action.
Mida sa teed?
What are you doing?
In this sentence, 'mida' functions as a relative pronoun introducing an indirect question.
Ma ei tea, mida ma vajan.
I don't know what I need.
In this context, 'mida' is used to introduce a clause describing the subject of the request.