Envy
Envy may be defined as an emotion that "occurs when a person lacks anothers superior quality, achievement, or possession and either desires it or wishes that the other lacked it."
It can also derive from a sense of low self-esteem that results from an upward social comparison threatening a person's self image: another person has something that the envier considers to be important to have. If the other person is perceived to be similar to the envier, the aroused envy will be particularly intense, because it signals to the envier that it just as well could have been him or her who had the desired object.
Bertrand Russell said envy was one of the most potent causes of unhappiness. It is a universal and most unfortunate aspect of human nature because not only does the envious person wish to inflict misfortune on others, but is also rendered unhappy by his envy.
Although envy is generally seen as something negative, Russell(1930, p. 90-91)also believed that envy was a driving force behind the movement towards democracy and must be endured in order to achieve a more just social system. The tendency to feel envy seems to be present in all cultures .

# Envy and jealousy
Envy and jealousy are distinct emotions. In its correct usage, jealousy is the fear of losing something that one possesses to another person (a loved one in the prototypical form), while envy is the pain or frustration caused by another person having something that one does not have oneself. Envy typically involves two people, and jealousy typically involves three people. Envy and jealousy result from different situations and are distinct emotional experiences. 

# Envy in philosophy
Aristotle (in Rhetoric) defined envy "as the pain caused by the good fortune of others", while Kant defined it as 
"a reluctance to see our own well-being overshadowed by another's because the standard we use to see how well off we are is not the intrinsic worth of our own well-being but how it compares with that of others" (in Metaphysics of Morals).

# Envy in the arts
In some cultures, envy is often associated with the color green, as in "green with envy". The phrase "green-eyed monster" refers to an individual whose current actions appear motivated by envy. This is based on a line from Shakespeare's Othello.  Shakespeare mentions it also in The Merchant of Venice when Portia states: "How all the other passions fleet to air, as doubtful thoughts and rash embraced despair and shuddering fear and green-eyed jealousy!" Envy is known as one of the most powerful human emotions for its ability to control one as if envy was an entity in itself. Countless men and women have fallen prey to brief periods of intense envy followed by anger which then translates into aggression. One of the most common examples is a pair of lovers in which a secret love is discovered and can lead to sorrow, then intense envy, and eventually anger and aggression.

# Envy in religion
Envy was one of the Seven deadly sins of the Christian Church.
The book of Exodus (20:17) states:
"Thou shalt not covet thy neighbours house; neither shalt thou desire his wife, nor his servant, nor his handmaid, nor his ox, nor his ass, nor any thing that is his."
Perhaps today the donkey (ass) corresponds to a car, but it could represent anything desirable owned by another. The donkey cannot be readily stolen as it would be obvious. However being envious of the donkey as a possession is to be avoided, as it could lead to ungodly thoughts or deeds toward the neighbour or the donkey.
It's important to make the distinction between desiring something someone else has, and envying them because of something they have. Envy relates to negative feelings toward a person because of something they own.