Emotion
An emotion, or emotional state, is a physical state which can either be a response to an external stimuli or the product of a memory. The state can either be positive or negative. In sentient species, the emotion can trigger a feeling. Emotions can be observed through facial expressions and body language. (; ; )

Emotions could be shared during mind melds, a process known as emotional transference. ()

In the Milky Way Galaxy, there are creatures which derive their nourishment from emotions. ()

Emotional expression 
Two species that are well known for suppressing their emotions are the Borg, with an exception of the Queen, and the Vulcans, with exception of the V'tosh ka'tur, and Sybok. ()

Vulcans were by nature a barbaric and savage people who came near self-annihilation, until the Time of Awakening; it was then when Surak preached the way of logic rather than emotion. (, ,  and others) Since Vulcans have the capability to exert a level of conscious control over virtually all of their body functions, they can actually manipulate the neural pathways that regulate and receive the balances of neurochemicals involved in emotion. This enables them to inhibit their brain from forming the neural impulses that create conscious emotional mental states, thereby actually suppressing their innate emotions. The psycho-suppression system in the Vulcan brain that endows Vulcans with this ability is located in the mesiofrontal cortex. () The Vulcan ritual, known as the kolinahr, is designed to purge all remaining emotions in a Vulcan. (; )

Despite their suppression of emotions, Vulcans still have them, and sometimes their violent nature resurfaces. Spock was vulnerable to polywater intoxication, and when he was infected, he was sobbing, having regretted his inability to express his love for his mother. Spock was also subject to the euphoria-inducing spores of the Omicron Ceti III pod plant. (, ) The Bendii Syndrome was an illness which makes elderly Vulcans lose their emotional control. () After a mind meld with Lon Suder, Tuvok's emotional system was traumatized, resulting in him losing some of his own control, becoming dangerous and violent. () In a later point, Tuvok laughed when his identity was erased to make him a laborer on the Quarren homeworld. () In addition, surprise, combined with strong emotion, made Spock (who was half-Human as well as half-Vulcan) lose control for a brief moment. ()

Contrarily, Odo has observed that the Bajorans are even less successful than most humanoids in hiding their emotions. () Humans obviously had emotions. ()

Often, robots like the Pralor Automated Personnel Unit or other advanced artificial lifeforms like androids or exocomps can exhibit self-awareness but don't have emotions. An exception is Data, who obtained an emotion chip from his creator, Dr. Noonian Soong, which allowed him to experience Human emotions. () After receiving the chip in 2371, he was initially unprepared for the unpredictable nature of emotions. However, that after having experienced 261 distinct emotional states, he felt he had learned how to control his feelings. () Although he was able to switch his emotions off he chose to remove the emotion chip in 2375. ()

Strong primitive emotions, like hate, can block a telepath's ability to read the mind of a person. As a prisoner of the Talosians, Vina attempted to block the Talosians from reading her mind for years with primitive emotions. Eventually, through fatigue coupled with the determination of her captors, she stopped trying. In 2254, Christopher Pike would, against the advice of Vina, attempt the same tactic against the Talosians. ()

Emotional states 
Admiration
Adoration
Affection
Anger
Anguish
Annoyance
Anticipation
Anxiety
Arousal
Awe
Benevolent 
Boredom
Brooding
Compassion
Concern
Courage
Curiosity
Depression
Desire
Despair
Desperation
Disappointment
Disgust
Distrust
Ecstasy
Embarrassment
Empathy
Enthusiasm
Envy
Euphoria
Excitement
Fear 
Frustration
Fun
Gratitude
Grief
Guilt
Happiness
Hate

Hostility
Humiliation
Infatuation

Jealousy
Joy
Kindness
Loneliness
Love
Loyalty
Lust
Optimism
Outrage
Panic
Passion
Pity
Pleasure
Pride
Protectiveness
Regret
Remorse
Resentment
Revenge
Sadness
Self-confidence
Self-pity
Sentimentality
Shame
Sorrow
Suffering
Surprise
Trust
Vanity
Wonder
Worry

Beings that feed on emotion 
Beta XII-A entity (hate, anger)
Drella (love)
Onaya (creativity)
Redjac (fear)

See also 
 Emotional baggage
 Kolinahr

External link 
 

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Psychology
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