sastavni

1. constituent; integral
   Sport je sastavni deo mog života. — Sport is an integral part of my life.
   Ugovor ima tri sastavna dela. — The contract has three constituent parts.
2. (in grammar) copulative; conjunctive
   Veznik „i” je sastavni veznik. — The conjunction "i" is a copulative conjunction.

Most often used in the phrase sastavni deo, "an integral part".