motivational (adj.)

1873, "act or process of furnishing with an incentive or inducement to action;" see motivate + -ion. Perhaps borrowed from German, where motivation is attested by 1854. Psychological use, "inner or social stimulus for an action," is from 1904.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).