Laziness is disinclination to activity or exertion despite having the ability to act or to exert oneself. It is often used as a pejorative; terms for a person seen to be lazy include "couch potato", "slacker", and "bludger". Related concepts include sloth, a Christian sin, abulia, a medical term for reduced motivation, and lethargy, a state of lacking energy.

Sloth is one of the seven deadly sins in Catholic teachings. It is the most difficult sin to define and credit as sin, since it refers to an assortment of ideas, dating from antiquity and including mental, spiritual, pathological, and conditional states. One definition is a habitual disinclination to exertion, or laziness. Views concerning the virtue of work to support society and further God's plan suggest that through inactivity, one invites sin: "For Satan finds some mischief still for idle hands to do.".