opportunity attack and different reach

just saw this 

How does a Reach weapon work with Opportunity Attack?

An Opportunity Attack is triggered when a creature you can see moves beyond your reach. If you want to make an Opportunity Attack with a Reach weapon, such as a Glaive or a Halberd, you can do so when a creature leaves the reach you have with that weapon. For example, if you’re wielding a Halberd, a creature that is right next to you could move 5 feet away without triggering an Opportunity Attack. If that creature tries to move an additional 5 feet—leaving your 10-foot reach—the creature then triggers an Opportunity Attack.

But crawford did state this If you have more than one reach, a foe provokes an opportunity attack when it leaves any of them. which means that even if you are carrying a halberd and they move five feet away they will trigger an unarmed opportunity attack, i never knew this before but will definately use it

Jeremy Crawford på X: "If you have more than one reach, a foe provokes an opportunity attack when it leaves any of them. #DnD https://t.co/tg4tGMDF0B" / X

That’s not what that means. A halberd has a reach of 10’, so you only provoke when moving more than 10’ away. 

More than one reach is something like dual wielding a short sword and a whip, where one has 5’ reach and the other 10’. In that case, moving from 5’ to 10’ would provoke an OA from the short sword. 
Also some monsters have things like a bite with a reach of 5’ and a claw with a reach of 10’. Same principle, moving from 5 to 10 would provoke from the bite. 

Quote from Xalthu >>

That’s not what that means. A halberd has a reach of 10’, so you only provoke when moving more than 10’ away. 

More than one reach is something like dual wielding a short sword and a whip, where one has 5’ reach and the other 10’. In that case, moving from 5’ to 10’ would provoke an OA from the short sword. 
Also some monsters have things like a bite with a reach of 5’ and a claw with a reach of 10’. Same principle, moving from 5 to 10 would provoke from the bite. 

You're agreeing with OP. Somebody with a halberd has multiple reaches, because you always have unarmed attacks.

I don't understand the purpose of this thread.

You get an opportunity attack if someone leaves your zone of control.  If you have a weapon that gives you a reach beyond the standard 5' you just have a larger zone of control.

So if an opponent moves and stays within your zone of control, why would you get an extra attack?  

Quote from jl8e >>

Quote from Xalthu >>

That’s not what that means. A halberd has a reach of 10’, so you only provoke when moving more than 10’ away. 

More than one reach is something like dual wielding a short sword and a whip, where one has 5’ reach and the other 10’. In that case, moving from 5’ to 10’ would provoke an OA from the short sword. 
Also some monsters have things like a bite with a reach of 5’ and a claw with a reach of 10’. Same principle, moving from 5 to 10 would provoke from the bite. 

You're agreeing with OP. Somebody with a halberd has multiple reaches, because you always have unarmed attacks.

 Ahhh. You’re right. I didn’t see the part about unarmed strikes. Thank you. 

Quote from Character77006 >>

I don't understand the purpose of this thread.

You get an opportunity attack if someone leaves your zone of control.  If you have a weapon that gives you a reach beyond the standard 5' you just have a larger zone of control.

So if an opponent moves and stays within your zone of control, why would you get an extra attack?  

"Zone of Control" is not a thing in D&D rules. Opportunity attacks are provoked by an enemy leaving your Reach. This thread is about what happens if you have more than one Reach, because you have multiple weapons that have different Reach stats.

As stated in the first post, if you have more than one Reach, an enemy provokes an opportunity attack from you if they leave any of those Reach distances, but the opportunity attack must be made with the weapon whose Reach they're leaving.

So, if you are wielding a Halberd (whose Reach is 10 feet) but you can also make Unarmed Strikes (whose Reach is 5 feet) you have more than one Reach. If an enemy is 2 feet away and moves to a position 7 feet away, they've left your Reach with your Unarmed Strikes, but they haven't left your Reach with your Halberd. You can therefore use your Reaction to make an opportunity attack with an Unarmed Strike, but not with your Halberd.

Thank for the ZOC correction.   Do you get an opportunity attack if you are not holding the weapon?  e.g. holding a 2 handed weapon with a 10' reach, but the battle axe with a 5' reach is not in your hands?

Quote from Character77006 >>

Thank for the ZOC correction.   Do you get an opportunity attack if you are not holding the weapon?  e.g. holding a 2 handed weapon with a 10' reach, but the battle axe with a 5' reach is not in your hands?

 no.

Quote from Character77006 >>

Thank for the ZOC correction.   Do you get an opportunity attack if you are not holding the weapon?  e.g. holding a 2 handed weapon with a 10' reach, but the battle axe with a 5' reach is not in your hands?

No. Your Reach is dependent on the weapon(s) you're wielding at the time.