In Islam, shirk (Arabic: شرك širk) is the sin of practicing idolatry or polytheism, i.e. the deification or worship of anyone or anything besides the singular God, i.e. Allah. Literally, it means ascribing or the establishment of “partners” placed beside God. It is the vice that is opposed to the virtue of Tawhid (monotheism). Those who practice shirk are termed mushrikun. Mushrikun (pl. of mushrik) are those who practice shirk, which literally means “association” and refers to accepting other gods and divinities alongside the god of the Muslims – Allah (as God’s “associates”). In Islamic law shirk as a crime, can just be attributed to Muslims, since only a Muslim is legally responsible not to associate any partner to Allah.
Within Islam, shirk is an unforgivable crime if it remains unpardoned before death: Allah may forgive any sin if one dies in that state except for committing shirk.
The word širk comes from the Arabic root Š-R-K (ش ر ك), with the general meaning of “to share”. In the context of the Quran, the particular sense of “sharing as an equal partner” is usually understood, so that polytheism means “attributing a partner to Allah”. In the Qur’an, shirk and the related word mušrikūn (مشركون)—those who commit shirk and plot against Islam—often refer to the enemies of Islam (as in verse 9.1–15).