Serotonin meaning

a compound present in blood platelets and serum, which constricts the blood vessels and acts as a neurotransmitter.

Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vasoconstriction 

विकिपीडिया 

Serotonin is the hormone that stabilizes our mood, feelings of well-being, and happiness

It is neurotransmitters for transferring massage through nerve and hormones for producing essential elements for body