The word(s) "adultery" appears 2 time(s) in 2 verse(s) in Quran in Saheeh International translation.

(1) And whoever among you cannot [find] the means to marry free, believing women, then [he may marry] from those whom your right hands possess of believing slave girls. And Allah is most knowing about your faith. You [believers] are of one another. So marry them with the permission of their people and give them their due compensation according to what is acceptable. [They should be] chaste, neither [of] those who commit unlawful intercourse randomly nor those who take [secret] lovers. But once they are sheltered in marriage, if they should commit adultery, then for them is half the punishment for free [unmarried] women. This [allowance] is for him among you who fears sin, but to be patient is better for you. And Allah is Forgiving and Merciful.

(2) And those who accuse their wives [of adultery] and have no witnesses except themselves - then the witness of one of them [shall be] four testimonies [swearing] by Allah that indeed, he is of the truthful.