“Are you single?” is “Ты свободна?” (“Ty svobodna?”) or “Ты не замужем?” (“Ty ne zamuzhem? ”) in Russian. You can ask like that if you address a woman. You should ask, “Ты свободен?” (“Ty svoboden?”) or “Ты не женат?” (“Ty ne zhenat?”), if you are talking to a man. “Single” also means “одинокий” (“odinokiy”). It has a negative connotation. It means “lonely”.
So it’s not polite and appropriate ask whether a person is lonely (“Ты одинок?”, “Ty odinok?” or “Ты одинока?”, “Ty odinoka?” if you ask a woman). Only if a person wants to answer like that themselves. “Ty zamuzhem?” – “Ya odinoka” (“Are you married?” “I’m single” (which can mean “lonely” in this case).
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