Zina is an Islamic legal term that refers to unlawful sexual intercourse. It is considered one of the most serious major sins in Islam, after shirk and murder. Zina encompasses any sexual intercourse except that between husband and wife, including extramarital sex and premarital sex. It is often translated as "fornication" in English. Technically, zina only refers to the act of penetration, while non-penetrative sex acts outside of marriage were censured by the Prophet as that which can lead to zina. Muslim scholars have historically considered zina a hudud sin, or crime against God. The punishment for zina varies according to whether the offender is muhsan (adult, free, Muslim, and married at least once) or not muhsan (i.e., a minor, a slave, a non-Muslim, or never married) . A person only qualifies as muhsan if he or she meets all of the criteria. The punishment for an offender who is muhsan is stoning (rajm), while the punishment for an offender who is not muhsan is 100 lashes.

It is important to note that zina is not only harmful for an individual Islamically, but it also poses a great danger to the whole society. Zina is responsible for increasing the burden physically, emotionally, socially, as well as economically on the individual who indulges with it. All religions are agreed that zina is haram, and no religion allows it. The sin of zina may be of varying degrees, and the gravity of the offense depends on the nature and circumstances of the deed, although all zina is haram, a major sin, and an act of immorality.

In summary, zina is an Islamic legal term that refers to unlawful sexual intercourse, including extramarital sex and premarital sex. It is considered one of the most serious major sins in Islam, and the punishment for it varies according to whether the offender is muhsan or not muhsan. Zina is not only harmful for an individual Islamically, but it also poses a great danger to the whole society.