Voluntary sexual intercourse with any person other than the spouse after the solemnization of marriage. Adultery is considered a serious matrimonial offense and a violation of marital fidelity.

• Essential: Proof of opportunity, inclination, and conduct leading to inference of adultery
• Standard of proof: Preponderance of probabilities, not beyond reasonable doubt (Dr. N.G. Dastane v. Mrs. S. Dastane, 1975)
• Defenses: Consent or connivance of petitioner; condonation (forgiveness with knowledge)

Both physical and mental cruelty are recognized grounds. Mental cruelty includes persistent insult, humiliation, false accusations, denial of conjugal rights without justification, causing mental pain and suffering.

• Examples: Repeated false allegations of infidelity, demanding dowry, refusal to have children, extra-marital affairs, verbal abuse
• Landmark: V. Bhagat v. D. Bhagat (1994) – Mental cruelty is conduct that causes such mental pain that it becomes impossible to live together
• No fixed definition — determined by conduct and impact on spouse's mental health

Willful abandonment of one spouse by the other without reasonable cause and without consent, with the intention to permanently separate (animus deserendi). Continuous period of at least two years immediately preceding the petition is required.

• Four essentials: separation, intention to desert, without consent, without reasonable cause
• Constructive desertion: refusing conjugal duties while living in same house
• Period of desertion excludes any time when parties resumed cohabitation

If a spouse ceases to be Hindu by converting to another religion (Islam, Christianity, etc.), the other spouse may seek divorce. Conversion alone does not automatically dissolve marriage; the other spouse must file a petition.

• Conversion must be voluntary and genuine
• After conversion, if the converted spouse marries again, that second marriage is void
• Conversion does not deprive inheritance rights from Hindu parents

The spouse has been suffering from a mental disorder of such a kind and to such an extent that the petitioner cannot reasonably be expected to live with the respondent. The disorder must be incurable or of a nature making cohabitation impossible.

• Requires medical evidence from qualified psychiatrist
• Schizophrenia, paranoia, bipolar disorder with severe symptoms may qualify
• Court may order medical examination of the spouse

If the spouse is suffering from leprosy that is both virulent (contagious/dangerous) and incurable, divorce may be granted. Modern medical advances have made leprosy treatable, so the bar is high.

• Medical certificate required from government hospital
• Not sufficient: leprosy that is under treatment or non-infectious form
• Must be incurable despite available medical treatment

The spouse is suffering from a venereal disease in a communicable form. The disease must be transmissible to the other spouse and should not have been contracted from the petitioner.

• Common examples: HIV/AIDS, Syphilis, Gonorrhea
• Disease must be in communicable stage at time of filing
• Petitioner must not have infected the spouse

If a spouse renounces the world by entering any religious order (Sanyas or formal renunciation), the other spouse can seek divorce. The renunciation must be complete and proven.

• Simple religious inclination is not enough
• Must be formal renunciation of all worldly ties
• Taking Sanyas diksha or joining religious order with vows of celibacy

If the spouse has not been heard of as being alive for a period of seven years or more by those who would naturally have heard of them, the spouse is presumed dead. The petitioner can file for divorce based on this presumption.

• Burden of proof on petitioner to show diligent inquiries for 7 years
• Presumption under Section 108 of Indian Evidence Act
• If absent spouse reappears, divorce decree may be set aside

If a decree of judicial separation has been passed and there has been no resumption of cohabitation for one year or more after the decree, either spouse may file for divorce.

• Allows conversion of judicial separation into divorce
• Parties must have lived separately after judicial separation decree
• No need to prove additional fault

When a decree for restitution of conjugal rights has been passed and there has been no resumption of cohabitation for one year or more after the decree, either party may file for divorce.

• Decree must have been passed by competent court
• No cohabitation for at least 12 months after decree
• Often used when one spouse obtains restitution order but other still refuses to cohabit