1.
Envy: From the Old French envie, 'envy'; the Latin invidere, 'to look at askance' or 'to see with malice', from in, a prefix connoting an intensification of the term modified, and videre, 'to look' or 'to see', hence 'to look intensively'; with the Latin root videre arising from the Greek eidos, 'form', and idea, 'appearance' or 'idea', and eventually the Sanskrit veda and vidya, expressing 'knowledge' and 'vision'. Both Matthew 27:18 and Mark 15:10 refer to the phthonon, 'envy' or 'ill-will', towards Jesus of the crowd that chose to have Barabbas freed instead of Jesus. There are a dozen references to envy in the non-Gospel portions.

2.
”To look at others and want what is theirs.”
The word envy comes from the Latin invidere, which means "to look at askance" or "to see with malice," and this sums up the sin quite nicely: envy, after all, is about looking at others and wanting what is theirs, whether it be status, abilities, or goods. Its seriousness has diminished as the concept of sin has weakened; envy used to be about a malevolent ill will towards another person, but the focus has shifted from the person to his possessions.
Thomas Aquinas, the medieval theologian, wrote: "Envy according to the aspect of its object is contrary to charity, whence the soul derives its spiritual life... Charity rejoices in our neighbor's good, while envy grieves over it." Dante grouped it with anger and pride as a sin of misdirected, or perverted love, because envy loves the possessions of others.
In Dante's Purgatorio, the envious are punished by having their eyes sewn shut so they can no longer look at others; Renaissance paintings depicted envy as a woman holding her entrails, or more often her heart, gnawing away. Undoubtedly it's this image which gave rise to the expression we use when we feel other should envy us: "Eat your heart out!"
Envy is unique among the Seven Deadly Sins in that it's only experienced in relation to other people, and it differs from greed in that it's about another person having something, rather than the thing itself. Envy and jealousy are often used interchangeably, but there's an important difference between the two: envy is about wanting what someone else has, while jealousy is the feeling you get when someone threatens what is yours.