Enmity (hate, sometimes erroneously called aggro) is the term for how likely a monster will focus on a specific player during combat.
Enmity is not to be confused with the term 'aggro' or 'link', which refers to a monster detecting a player, and engaging them.
To be able to gain enmity, to be on a monster's "enmity list", a player either has to perform an action on the monster itself (cast a spell on it, or attack it), or perform an action on someone who is already on the monster's "enmity list".
Significant player testing indicates that the total amount of enmity for a player consists of two components, a static form of enmity (referred to as cumulative enmity), and a dynamic form of enmity (volatile enmity).
Examples Enmity+20 = 120%, or 1.2x normal Enmity gain. Enmity+50 = 150%, or 1.5x normal Enmity gain.
Enmity-10 = 90%, or 0.9x normal Enmity gain.