stimulus

noun (plural stimuli /-lʌɪ, -liː/)

• a thing or event that evokes a specific functional reaction in an organ or tissue:areas of the brain which respond to auditory stimuli
• a thing that arouses activity or energy in someone or something; a spur or incentive:if the tax were abolished, it would act as a stimulus to exports
• [in singular] an interesting and exciting quality:she loved the stimulus of the job