stimulus

an economic stimulus

Even light nonpainful stimuli can provoke or exacerbate spontaneous pain; this is not limited to tactile, thermal, or vibratory stimuli, because auditory, visual, olfactory, and visceral stimuli also may be problematic.

Many plants, like many animals, are furnished with arms for their protection; these are either aculei, prickles […] ; or stimuli, stings, as in the nettles, which are armed with a venomous fluid for the annoyance of naked animals.