柯林斯詞典serotonin /?s?r??t??n?n/ 1. N-UNCOUNT Serotonin is a chemical produced naturally in your brain that affects the way you feel, for example, making you feel happier, calmer, or less hungry. 血清素 返回 serotonin劍橋詞典a neurotransmitter (= a chemical in the body that carries messages from the brain ) that helps you feel relaxed and happy 血清素 返回 serotonin