The following is wikipedia's definition of "greed", and my notes of it:

Greed typically denotes the excessive urge to possess as a goal bringing satisfaction in itself, the desire to acquire material wealth and possessions beyond the need of the individual, especially when this accumulation of possession denies others legitimate needs or access to those or other resources.

principal characteristics of greed: human nature in the form of urge or desire

criteria of greed: 1. acquisition beyond an individual's need, 2. denying others' legitimate needs

For example, amassing a large collection of coins would not in itself be considered greed, unless the needs of others were jeopardized in the process. Essential to the concept of greed is the awareness that the needs of others are denied, thus rivalrous goods exemplify greed while non-rivalrous goods may not.

essencial property of greed: awareness of the denial of others' needs

Greed also often involves using wealth to gain power over others, sometimes by denying others wealth or power.

goal of greed may involve the acquisition of power -- the criterion of denial to others as above applies

Some desire to increase or maintain one's wealth is more or less universal and acceptable in any culture, but this simple want is not enough to be considered greed.

greed is not want

Greed is the far end of this desire, particularly where one desires things simply for the sake of owning them (such as the desire to have great amounts of money not to purchase objects, but where the possession of the money is an end unto itself).

greed is the desire to own or possess, not the intent to use or apply

Greed typically entails acquiring material possessions at the expense of others' welfare; for example, a father buying himself a new car, rather than fixing the roof of the family home, or otherwise a case of morally wrong priorities.

greed often involves misprioritized goals of one's intent

Greed (by extended definition) for the consumption of food or drink for pleasure, combined with excessive indulgence in them, is called gluttony;

gluttony is a form of greed involving food and drink

similarly, excessive greed for and indulgence in sex may be called lust, although it is generally understood that the latter term often no longer carries such negative connotations as it once did.

lust is another form of greed involving sex