Hit

The term hit refers to an effect that applies a discrete amount of damage to a target instantaneously. The damage can be mitigated down to 0, but can never be negative. Damage dealt by hits always has one of 3 damage sources (attack, spell or secondary, but note that damage over time never hits. ) and is combined of any 5 damage types (physical, fire, cold, lightning or chaos).

Besides the amount of damage, its type and source, 'hit packages' also contain certain mechanics and effects, such as: and others.
 * critical strikes
 * ailments
 * penetration and resistance ignoring (i.e. Inevitable Judgement)
 * accuracy (for attacks only)
 * modifications to target's block and dodge chances (i.e. )

On/when hit effects
"On Hit" effects are when the player hits the enemy, and "When Hit" is when the enemy hits the player. In general, most effects are applied after the hit is completed and damage is dealt, since magnitude of damage is used to compute the magnitude of effect. These include, but are not limited to:
 * gain temporary buffs (e.g. charges)
 * inflict debuffs (e.g. curses or bleed)
 * stun
 * knockback
 * gain life, mana or energy shield
 * culling strike
 * skill-specific effects (e.g. 's explosion).

Additionally, some effects have specific requirements, such as only working with attacks, culling strike only affects enemies with less than 10% life, and 's effect needing a critical strike.

Conditional modifiers
There are modifiers that can only apply their effects when a certain condition is met. Modifiers that are conditional on properties of the target do not affect damage over time because only hits are able to check someone else properties. For example, from  doesn't increase damage from DoTs.

gloves will prevent your hits from killing enemies who are not frozen. This will not stop enemies from dying from your damage over time or minions.

Items that enable self-damaging
Items that hit:
 * (on use)
 * (on igniting an enemy)
 * (on using a movement skill)
 * (on minion death)
 * (on skill use)

Items that do not hit, but still deal damage to you:
 * (on kill)
 * (on kill)
 * (on kill)
 * (on kill)
 * (on kill)
 * (on kill)