activator, aggravation, agitation, animation, animator, antecedents, arousal, arouser, arousing, bait, base, basis, boost, bribe, call, carrot, catalyst, causation, cause, cause and effect, determinant, determinative, electrification, element, encouragement, energizer, etiology, exacerbation, exasperation, excitation, excitement, exhilaration, factor, fillip, fomentation, galvanization, goad, ground, grounds, human dynamo, impetus, impulse, incentive, incitation, incitement, inducement, inflammation, infuriation, instigation, interest, invitation, irritation, lathering up, life, lure, motivating force, motivation, motive, motive power, occasion, payment, percentage, persuasive, perturbation, principle, profit, propellant, provocation, provocative, push, restorative, reward, spark plug, spur, steaming up, stimulant, stimulation, stimulative, stimulator, stirring, stirring up, sweetener, sweetening, tonic, urging, whet, whipping up, working up