This is the 62nd most frequent Macedonian word.
си
"Си" in Macedonian means "yourself" or "you are" (reflexive pronoun or auxiliary verb, depending on context).
In this sentence, 'си' represents the second-person singular present tense form of the verb 'сум' (to be), indicating the subject 'you'.
Ти си многу умен.
You are very smart.
Here, 'си' functions as a reflexive pronoun intensifier, representing emphasis or involvement by the subject in the action of the verb.
Си купив нова книга вчера.
I bought a new book yesterday.
In this usage, 'си' conveys thinking or personal mental activity as part of a colloquial construction.