Types of Crowd Control

There are three fundamentally different categories of crowd control, with most specific forms of CC falling under one or more of them.
 * Movement Modifiers restrict or reduce the target's movement or force a particular move.
 * Slows, Snares, Knockbacks
 * Action Modifiers restrict the target's ability to perform some actions or reduce those actions' effectiveness.
 * Blinds, Silences, Stuns, Knockups, Suppresses
 * Forced Action Modifiers force the target to take a certain action.
 * Taunts, Fears

Types of crowd control
These are the specific types of crowd control that appear in League of Legends along with a few key notes about each.
 * Blind
 * Makes the target always miss with auto attacks.
 * Has no effects on most abilities and will not interrupt them or prevent their damage.
 * Some empowered auto-attacks like Siphoning Strike will miss if target is blinded.
 * The damage of Infinite Duress will miss if Warwick is blinded before casting and during its duration.
 * The damage from judgement will miss if Garen is blinded during the use of the ability.
 * Champions with Blind: ,
 * Fear
 * Forces the target to run around randomly.
 * Prevents controlled movement, auto attacks, and the use of abilities.
 * Will interrupt channeled abilities.
 * Champions with Fear:, ,
 * Knockback
 * Pushes one or more units to a different spot against their will.
 * Will interrupt channeled abilities.
 * Cannot be removed by or reduced by Tenacity.
 * Champions with Knockback: ,, , , , , , ,
 * Knockup
 * Knocks the target into the air but does not change their location.
 * Prevents movement, auto attacks, and the use of abilities while in the air.
 * Will interrupt channeled abilities.
 * Cannot be removed by or reduced by Tenacity.
 * Champions with Knockup:, , , , , , , ,
 * Silence
 * Prevents use of most spells and abilities.
 * Does not stop auto attacks.
 * Will interrupt channeled abilities.
 * Champions with silence: ,, , , , , , ,
 * Slow
 * Reduces movement speed.
 * Champions with slow:,, , , , , , , , , , , , , , , , , , , , ,     , , , , , , , , , , , , , , , , , , , , ,
 * Snare (Root, Immobilize)
 * Immobilizes to prevent movement entirely.
 * Also prevents movement abilities (dashes, blinks and teleports)
 * Champions with Snare: ,, , , , , ,
 * Stun
 * Immobilizes and prevents actions.
 * Will interrupt channeled abilities.
 * Blocks use of most abilities.
 * Champions with Stun:, , , , , , , , , , , , , , , , , , , , , , , ,
 * Suppression
 * Immobilizes and prevents actions.
 * Will interrupt channeled abilities.
 * Prevents use of most abilities, including summoner spells.
 * Cannot be removed by or reduced by Tenacity.
 * Champions with Suppression: ,, ,
 * Taunt
 * Forces the target to try to auto attack the taunting champion, making him unable to do anything else.
 * Will interrupt channeled abilities.
 * Can force movement because target will chase to try to autoattack while taunting.
 * Champions with Taunt: , ,

Removing

 * The summoner spell removes all CC except suppression and knockup.
 * , removes all forms of CC including suppression, except knockup.
 * The active on removes all forms of CC including suppression, except knockup.
 * removes all forms of CC including suppression, except knockup.
 * ( will continue to do damage.)
 * removes all slows. It also reduces the duration of new slows by 50% for the duration of the ability.

Preventing

 * prevents all forms of CC for 5 seconds or until the shield is broken.
 * prevents all CC except blinds and silences for (5/6.5/8) seconds.
 * prevents slows for (6/9/12) seconds.
 * creates a magical barrier which blocks a single enemy ability used on Sivir.
 * creates a magical shield for 2 seconds which can block the next enemy spell that hits him.

Reducing
Note: Duration reduction has no effect on suppression, knockup, or knockback.

Tenacity
The reduction from the Tenacity stat on items does not stack with itself and stacks multiplicatively with other types of CC duration reduction from the champion abilities.
 * reduces the duration of CC by 35%.
 * reduces the duration of CC by 35%.
 * reduces the duration of CC by 35%.
 * reduces the duration of CC by 35%.

Champion abilities

 * reduces the duration of CC while active by (15/20/25/30/35)%.
 * reduces the duration of CC by (10/25/40)% for (1/2/3) nearby enemy champion(s).
 * reduces the duration of CC by (10/20/30)% for 25 seconds.
 * reduces the duration of CC while active by (20/25/30/35/40)%.