辣是化学物质（譬如辣椒素、姜酮、姜醇等）刺激细胞，在大脑中形成了类似于灼烧的微量刺激的感觉，不是由味蕾所感受到的味觉，而是一种痛觉。所以其实不管是舌头还是身体的其他器官，只要有神经能感觉到的地方就能感受到辣。

四川人和湖南人很多都爱吃辣，他们认为吃辣可以去湿。当人习惯吃辣后，并会对辛辣食物有了依赖性，自此无辣不欢。

其次，辣也可以表示一种极端刺激的感觉或感受。譬如《红楼梦》的人物王熙凤，她的绰号就叫“凤辣子”，就是形容她为人尖锐，有如辣味一样给别人一种强烈的冲击感。所以汉语中也有很多词语包含“辣”字、但和平常所说的触觉不相干的，例如泼辣、狠辣、毒辣、心狠手辣等。

Pungency is the condition of having a strong, sharp smell or taste that is often so strong that it is unpleasant. Pungency is the technical term used by scientists to refer to the characteristic of food commonly referred to as spiciness or hotness and sometimes heat, which is found in foods such as chili peppers.