The word "emotion" comes from the Latin emovere which means "to set in motion". Initially it referred to the idea of physical movement and a figurative meaning associated with mental movement.

Wikipedia defines "emotion" as a "complex reaction pattern, involving experiential, behavioral, and physiological elements, by which the individual attempts to deal with a personally significant matter of event". It arises without conscious effort and is either positive or negative in its valence.

In 1980, the psychologist Robert Plutchik defined a list of basic emotions and basic opposites composed of joy - sadness, acceptance - disgust, fear - anger, surprise - anticipation and a list of 8 advanced emotions composed of 2 basic ones.

Optimism: anticipation + joy
Love: joy + acceptance
Submission: acceptance + fear
Awe: fear + surprise
Disappointment: surprise + sadness
Remorse: sadness + disgust
Contempt: disgust + anger
Aggressiveness: anger + anticipation

More emotions: acceptance, affection, aggression, ambivalence, anger, apathy, anxiety, compassion, depression, disgust, doubt, ecstasy, empathy, envy, embarrassment, euphoria, fear, forgiveness, frustration, guilt, gratitude, grief, happiness, hatred, hope, horror, hostility, homesickness, hysteria, loneliness, love, paranoia, pity, pleasure, pride, rage, regret, remorse, sadness, shame, suffering, surprise, sympathy.

Since emotions are abstract and subjective, they remain difficult to quantify.

Related terms are affect, disposition, feeling, mood.