Will, volition, conation can all refer to the power or act of making or effecting a choice or decision.
Will applies not only to this power or act but also to the complex of rational and irrational, conscious and unconscious forces within a person that is the agent of this power and to the process by which one makes his choice, resolves it into an intention, and puts that intention into effect.
In all of these senses will may vary greatly in its specific meaning; it may denote a dominant desire or inclination which determines one’s choice or it may denote a power that derives from one’s conception of what is good or right and that tests and accepts or rejects one’s desires or inclinations.
Will often denotes mainly the determination that is inseparable from action or the effecting of one’s decisions, but it may be used when frustration or impossibility of action is suggested <spirits disillusioned, who still pathetically preserve the will to conquer, even when life no longer presents them with anything worth winning —Binyon > Further will may designate a subjective power, act, or process or an objective force which must be encountered, challenged, or obeyed.
Volition , in contrast to will , is a comparatively simple term. In its ordinary and most sharply distinguished sense, it designates merely the act of making a choice or decision; it usually carries an implication of deliberation, but it rarely suggests struggle or determination to put one’s decision or choice into effect. Therefore it may be preferred when no other implications are desirable or important.
Conation usually implies a striving to get or achieve what is desired or willed. The term need not imply a conscious goal; it may suggest clearly directed striving or it may connote the restless aimless strivings which the mind cannot interpret or explain, but it stresses effort rather than choice.