Noxious stimulus
A noxious stimulus is "an actually or potentially tissue damaging event."[1] It is a prerequisite for nociception, which itself is a prerequisite for nociceptive pain.[1]
Noxious stimuli can either be mechanical (e.g. pinching or other tissue deformation), chemical (e.g. exposure to acid or irritant), or thermal (e.g. high or low temperatures).
There are some types of tissue damage that are not detected by any sensory receptors, and thus cannot cause pain. Therefore, not all noxious stimuli are adequate stimuli of nociceptors. The adequate stimuli of nociceptors are termed nociceptive stimuli. A nociceptive stimulus is defined as "an actually or potentially tissue damaging event transduced and encoded by nociceptors."[1]