A vice is a practice, behavior, or habit that is generally considered wrong in a society. It can refer to a fault, a negative character trait, a defect, an infirmity, or a bad or unhealthy habit. Vices are usually associated with a fault in a persons character or temperament rather than their morality. Synonyms for vice include fault, sin, depravity, iniquity, wickedness, and corruption. The antonym of vice is virtue.

Vices can be categorized into different types, such as moral vices, physical vices, and animal vices. Moral vices refer to behaviors that are considered immoral or unethical, such as greed, pride, envy, and lust. Physical vices refer to physical imperfections, deformities, or taints. Animal vices refer to abnormal behavior patterns in domestic animals that are detrimental to their health or usefulness.

In law enforcement and judicial systems, the term vice is often used as an umbrella for crimes involving activities that are considered inherently immoral, regardless of the legality or objective harm involved. Depending on the country or jurisdiction, vice crimes may or may not be treated as a separate category in the criminal codes. In the United Kingdom, the term vice is commonly used in law and law enforcement to refer to criminal offenses related to prostitution and pornography. In the United States, the term is also used to refer to crimes related to drugs, alcohol, and gambling.