“Free” is “бесплатный” (“besplatniy”) or “бесплатно” (“besplatno”) in Russian. “Freebie” is “задаром” (“zadarom”). You can use the word “халява” (“khalyava”) for it with your friends or buddies. If you use “free” with a noun it’s “бесплатный”. For instance, “I got a free ticket” is “Я получил бесплатный билет” (“Ya poluchil besplatniy bilet”). “I got it for free” is “Я достал это бесплатно” (“Ya dostal eto besplatno”). “Besplatno” is an adverb. “This service is free” is “Эта услуга бесплатная” (“Eta usluga besplatnaya”).