The act of inclining or the state of being inclined; a bend or tilt: The inclination of the child's head suggested sleep. A deviation or the degree of deviation from the horizontal or vertical; a slant: the steep inclination of a roof. The angle between two lines or planes: the inclination of the comet's orbit with respect to that of Earth. An inclined surface; a slope. A characteristic disposition or tendency to act in a certain way; a propensity:"I shall indulge the inclination so natural in old men, to be talking of themselves"(Benjamin Franklin). A preference or liking: his musical inclinations.