Emotion: Specific feeling that disposes one to act in certain ways because it serves as end.
Not all feelings are emotions, and not all emotions are preparations to act: An emotion, rather than a preparation to act, is a state of feeling, a state of oneself, or a state of the world that one desires (or fears) for some reason. (One can regiment the fears under desires for their denial.) That reason may be an easy to understand human need, like hunger, or it may be a difficult to understand ideal, like pacifism, the Millenium, mystical enlightenment, or Divine Blessing, but in any case there is an emotion there will be some end in view and some feeling for or against it that motivates one that way.
It makes sense, by an large, to reserve the term 'emotion' for such end-directed feelings that involve some personally held theory about the world or oneself or others, that as a rule depend on values, and to use the term 'feeling' especially for such states of pleasure or displeasure that relate to innate bodily needs, though it is clear there always will be some overlap.