You have to interrupt when an attack of opportunity presents itself and use your reaction for the round to make the attack of opportunity. Most attacks of opportunity come when an opponent moves out of your reach, so if you wait until your turn that opponent will have moved and acted. An attack of opportunity can kill the opponent and prevent that opponent from attacking and killing someone, healing, etc..
I haven't heard of opportunity actions, but there are a few spells which are cast as reactions. Shield is one of them and another one is Hellish Rebuke. They're immediate and they interrupt the normal flow of a round of combat.
You can use your reaction to make an opportunity attack when an enemy you can see is about to leave your reach. A DM might choose to be proactive and ask if you want to take one, but they don't have to. You're within your rights to interrupt the monster's turn and declare your opportunity attack if you meet all the requirements.
There's no such thing in the rules as an opportunity action.
Opportunity Action someone was probably referring to Ready actions. On your turn you may use your Action to Ready an Action to be used as a Reaction. For instance you say, I am "Ready to smash the thing if he enters the room." Then if you see him enter the room you may smash the thing immediately, even though it is not your turn.
So in the course of actual gameplay, how are opportunity attacks announced?
Do I interrupt the dialog when the OA presents itself?
Do I wait till my turn to say I'm making an OA?
Also, I've heard of opportunity ACTIONS. What are they?
You have to interrupt when an attack of opportunity presents itself and use your reaction for the round to make the attack of opportunity. Most attacks of opportunity come when an opponent moves out of your reach, so if you wait until your turn that opponent will have moved and acted. An attack of opportunity can kill the opponent and prevent that opponent from attacking and killing someone, healing, etc..
I haven't heard of opportunity actions, but there are a few spells which are cast as reactions. Shield is one of them and another one is Hellish Rebuke. They're immediate and they interrupt the normal flow of a round of combat.
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You can use your reaction to make an opportunity attack when an enemy you can see is about to leave your reach. A DM might choose to be proactive and ask if you want to take one, but they don't have to. You're within your rights to interrupt the monster's turn and declare your opportunity attack if you meet all the requirements.
There's no such thing in the rules as an opportunity action.
The Forum Infestation (TM)
Opportunity Action someone was probably referring to Ready actions. On your turn you may use your Action to Ready an Action to be used as a Reaction. For instance you say, I am "Ready to smash the thing if he enters the room." Then if you see him enter the room you may smash the thing immediately, even though it is not your turn.
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