Natural inclination is an innate behavior or TENDENCY that is often difficult to explain. INSTINCT, with 8 letters, is an inborn pattern of behavior that is present in all members of a species and is not learned. BENT, with 4 letters, is an inclination or predisposition towards something, usually in a negative sense. Lastly, TENDENCY, with 8 letters, is a general direction of change or a predisposition to a certain behavior or outcome. All of these terms can be used to describe a natural inclination.