Русско-англо-русский юридический словарь

Grounds for divorce in countries consider adultery as the most common grounds for divorce. (Wikipedia)

Adultery (anglicised from Latin adulterium) is extramarital sex that is considered objectionable on social, religious, moral or legal grounds. Though what sexual activities constitute adultery varies, as well as the social, religious and legal consequences, the concept exists in many cultures and is similar in Islam, Christianity and Judaism. (Wikipedia)

Currently, one spouse must allege adultery or unreasonable behaviour by the other for divorce proceedings to start straight away. (BBC News)

The grounds for divorce are:

• • 1 year of separation
• • adultery
• • mental or physical cruelty