According to S.375, I.P.C., all of the following are considered as rape, EXCEPT:
Sexual intercourse by a man with his own wife (even against her will) is not rape, if she is above 15 years of age. A man is said to commit rape, if he has sexual intercourse with a woman with or without her consent, when she is under 16 years of age. Ref: The Essentials of Forensic Medicine and Toxicology by Dr K. S.Narayan Reddy, 27th edition, Page 351.
Wife of another person
Own wife below 15 years
Age below 16 years of age
Against wife's consent