motive >> ˈməʊtɪv
Definition: [noun] a reason for doing something.
Example: police were unable to establish a motive for his murder
Definition: [noun] a motif in art, literature, or music.
Definition: [adjective] producing physical or mechanical motion.
Example: the charge of gas is the motive force for every piston stroke
Definition: [adjective] causing or being the reason for something.
Example: the motive principle of a writer's work