Does a player character's attack from the "Attack" action have a reach?

Question

While discussing this answer I made to a recent question concerning the Bugbear's Long Limbed trait and how the reach bonus affects the character's other reach-related effects, this question naturally rose. Since both sides seem plausible for now, I decided to ask away as a separate question.

On one side, for player character attacks, the only mention of reach I could find in the books were the player character's reach, which seems to be considered as a stat owned by the player character and separate from the attacks one may take during combat.

On the other hand, a monster's attacking actions are described with the following :

Certain creatures [...] have melee attacks with a greater reach than 5 feet, as noted in their descriptions.

This could imply that a creature's melee attack action could have its own reach property. While this may support the idea that an attack may have its own reach property, potentially separated from the creature's reach stat, the argument that a monster's offensive actions are different from a player character's Attack action also makes sense.

So, the question is the following: does a player character's attack, made using the Attack action, have its own reach, or is any reach used by this attack the player character's own reach?

A good answer will have citations from the books showing either definite, or in the lack thereof, tentative proof of the most plausible output to this question. Bonus points if both sides of the debate are covered.

Answer 1

Your every attack has its own reach

Reach of an attack is always based on the reach of the character that’s making the attack, it doesn’t exist independently just as the attack doesn’t, it’s always made by someone. It doesn’t have to be the same as character’s general reach though and there are features that affect the reach of individual attacks, suggesting that each attack has its own reach.

To back it up, let’s have a look at a few features that increase character’s reach and how they’re worded:

• Reach Weapons - This weapon adds 5 feet to your reach when you Attack with it (…)
• Potion of Giant Size - (…) In addition, the reach of your melee attacks increases by 5 feet.
• Fangs of the Fire Snake (Way of Four Elements Monk) - (…) Your reach with your unarmed strikes increases by 10 feet for that action (…)
• Long-Limbed - When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.

As can be seen, none of those features simply increase character’s reach, they all very specifically refer to the attack itself. This suggests quite strongly that attacks do have their own reaches.

For example, let’s take the first one, the Reach property of a weapon. It lets you add 5 feet to the attack’s reach when attacking with it, so if you attack with, say, a Halberd on your turn, then drop it on the ground and in your next turn attack with a Dagger, your first attack will have a reach of 10 feet but the second one will only have 5 feet.

Answer 2

The rules seem to treat your reach and your reach for a particular attack as separate statistics.

Reach is poorly defined, unfortunately. It is never explicitly defined for small and medium sized player characters. Instead, the combat rules give us this helpful gem (PHB, pg. 195):

Most creatures have a 5-foot reach and can thus attack targets within 5 feet of them when making a melee attack. Certain creatures (typically those larger than Medium) have melee attacks with a greater reach than 5 feet, as noted in their descriptions.

These two sentences talk about creatures having a reach, as well as melee attacks having a reach. Next, let us examine the Reach property:

Reach. This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.

Once again, this rule makes a distinction between your reach and your reach with a particular attack. A Reach weapon adds five to your reach when you attack with it, but it does not add to "your reach". If it simply added to your reach, the line about determining your reach for opportunity attacks would be unnecessary. Instead, it changes your reach only for the purposes of determining your reach for opportunity attacks, but it doesn't flatly modify "your reach".

There are other features that make a distinction, such as the one you mention, the Bugbear's Long Limbed feature:

When you make a melee attack on your turn, your reach for it [the attack] is 5 feet greater than normal.

Once again, this feature modifies your reach only for a specific attack. And there are several other features that read similarly.

In contrast, there is at least one feature that flatly increases your reach. Rolling 51-55 on the Flesh Warping table in Baldur's Gate: Descent into Avernus has the following effect:

The target’s arms become tentacles with fingers on the ends, increasing its reach by 5 feet.

While under this effect, your reach that is normally five feet is now ten feet for all purposes.

Therefore, your reach may be different from your reach for a particular attack, depending on what features are in play. However, this probably doesn't apply to NPCs and monsters where the only place their reach is ever defined is in their attack descriptions.