Emotions are objective, clear and well-defined mental and physical states such as anger, joy, fear and sadness. Our thoughts trigger chemical changes in the brain that lead to chemical and physiological changes in the body. All of these changes are interpreted as specific emotions based on the external context.

An increase in the levels of norepinephrine, epinephrine and cortisol is interpreted as fear or anger. Aggression is linked to low serotonin as a neurotransmitter and high testosterone. Pleasure and reward are associated with increased dopamine levels as a neurotransmitter. Depression is clinically associated with decreased levels of monoamine neurotransmitters dopamine, norepinephrine and especially serotonin. Oxytocin is associated with trust and love.

So, emotions are cocktails of different neurotransmitters and hormones and different proportions of the same chemicals can create different emotions.