ATTACK of OPPORTUNITY
You threaten all squares into which you can make a melee attack, even when it is not your turn. Generally, that means everything in all squares adjacent to your space (including diagonally). An enemy that takes certain actions while in a threatened square provokes an attack of opportunity from you and you can attack them in their own turn, even if it is not your own turn, before they move away. If you’re unarmed, you don’t normally threaten any squares and thus can’t make attacks of opportunity. An attack of opportunity is a single melee attack, and you can only make one per round. You don’t have to make an attack of opportunity if you don’t want to.
Feat: Universal
Damage Type: Melee
Save: Reflex 1/2
Counter: AC, Dodge, Defense ...
Use: Free Action
Rank 1:
Number of Attacks of Opportunity per round: 1
Target's Actions that provoke Attacks of Opportunity: Move Action
Rank 2:
Number of Attacks of Opportunity per round: 2
Target's Actions that provoke Attacks of Opportunity: Move Action
Rank 3:
Number of Attacks of Opportunity per round: 3
Target's Actions that provoke Attacks of Opportunity: Move Action
Rank 4:
Evolution A: Attacks of Opportunity per round: +1
Evolution B: +Standard Action: Tech Ability Activation
Rank 5:
Evolution A: Attacks of Opportunity per round: +1
Evolution B: +Standard Action: Force Power Activation
Evolution C: BAB now affects how many attacks you can make in each Attack of Opportunity
Sometimes a combatant in a melee lets his guard down. In this case, combatants near him can take advantage of his lapse in defense to attack her for free. These free attacks are called attacks of opportunity.