Had a couple questions regarding Reactions, specifically Sentinel and Opportunity Attacks. Wasn't 100% sure so thought best to clarify

1) am I correct in assuming I can make multiple OA's per round, against every enemy that moves out of 5ft? Eg 1 orc moves away and I make an OA, then another moves past me to attack someone else but passes through that 5ft I can make another OA against that second orc?

2) if I make an attack using Sentinel against an orc attacking one of my party, can I then make an OA against an orc that was fighting me moves out of my 5ft reach?

3) if I have a member of my party either side of me, can I use Sentinel both times if each of those party members is attacked? 

4) if an enemy has multiple attacks, am I correct in assuming I can only use Sentinel once, or for each attack?

Quote from Mikkleecosplay >>

Had a couple questions regarding Reactions, specifically Sentinel and Opportunity Attacks. Wasn't 100% sure so thought best to clarify

 

1) am I correct in assuming I can make multiple OA's per round, against every enemy that moves out of 5ft? Eg 1 orc moves away and I make an OA, then another moves past me to attack someone else but passes through that 5ft I can make another OA against that second orc?

2) if I make an attack using Sentinel against an orc attacking one of my party, can I then make an OA against an orc that was fighting me moves out of my 5ft reach?

3) if I have a member of my party either side of me, can I use Sentinel both times if each of those party members is attacked? 

4) if an enemy has multiple attacks, am I correct in assuming I can only use Sentinel once, or for each attack?

 

Basically, no.  Once you take a Reaction, you cannot take another until the start of your next turn.  So no multiple AoO's between your turns, as each one requires a Reaction.  You can get 2 AoO's in a single round, assuming you haven't used one after your turn in the previous round: the first one comes before your turn and the other comes after, but both in the same round.

Player's Handbook: "When you take a reaction, you can't take another one until the start of your next turn."

So, to clarify (according to my interpretation of official rules):

1. Mostly, no - maximum two turns in a single round, one before your turn starts if you haven't used a reaction already, and one after your turn... which obviously, falling under rule quoted, is still one until the start of your turn, because you can only do it once if you're constantly using your reactions.

2. No - once you use a reaction (for an opportunity attack or via a feat) you've used your reaction. 

3. No - you have to pick and choose, and if one of the other party members has Sentinel, it might not activate for them, as per Sentinel's wording.

4. One reaction until the start of your next turn. Basically just once. 

(So how you're hoping to spam Sentinel as your questions implied is not possible, unless your DM has a houserule that is different. Personally, I would find it terrifying to play at a table where unlimited reactions exist. Imagine being sure your spell can't be counterspelled by the enemy spellcaster because they've used their reaction on another player's turn - only for it to be shot down by the second counterspell by that same spellcaster and it wastes your spellslot.)

Hope this helps!

Thanks for clarifying, it's my first time ever going for a melee heavy character, I'm used to staying at the edges so just wanted to make sure I understood correctly

Just for completeness' sake, there is an exception to this. The level 18 Cavalier feature allows you to make an Opportunity attack on every creature's turn except yours. But even in that case the answers to 2, 3, and 4 would be no because the triggers occur on the same creature's turn.