causing physical irritation or a stinging sensation; pungent; spicy

A chemical substance produced in the body that regulates growth, metabolism, and other biological processes.

Any substance that excites the body's sensory organs or systems, such as alcohol, tobacco, or caffeine; stimulant; stimulus

(immunology) costimulation; costimulatory

a chemical agent or poison that causes irritation or damage to the lungs and respiratory system

a substance or stimulus that increases physiological or nervous activity

something that causes a physical or mental reaction; stimulant

A stimulus that triggers a [[条件反射|條件反射|tiao2 jian4 fan3 she4]].