Shirk (Arabic ΤΡί) is the Islamic concept
of the sin of polytheism specifically, but in a more general way
refers to serving anything other than the One
God; i.e. wealth, lust, the ego, etc.
It is the vice which is opposed to the virtue of
tawhid, literally "declaring [that
which is] one", often translated into the English theological
term "monotheism." The word is not related to the English verb "shirk"
related to neglect.