Can an area of effect spell cause damage to the same target multiple times a round? [duplicate]

Question

Yesterday, I asked a question regarding the spell Sickening Radiance. The most upvoted answer satisfied the question, but it also added this small line:

Yes, forcefully moving enemies into the area does cause them to be affected by the spell.

Note, however, that in that case they would not also be affected on their turn. Sorry, no 8d10 damage per round here...

I don't see anything that would make this the case, yet it is upvoted (as of writing) five times, hence this question.

Sickening Radiance states:

When a creature moves into the spell's area for the first time on a turn or starts its turn there, that creature must succeed on a Constitution saving throw or take 4d10 radiant damage [...]

As far as my understanding goes, a turn and a round are two explicitly defined different things by the PHB:

The game organizes the chaos of combat into a cycle of rounds and turns. A round represents about 6 seconds in the game world. During a round, each participant in a battle takes a turn. (PHB, 189)

So, to give an exact example, let's say an enemy is pushed into Sickening Radiance and is affected by the spell ("moves into the spell's area of the first time on a turn"). If during the same round, the enemy's turn starts inside of it ("or starts its turn there"), are they affected again?

Answer 1

The wording of the spell is:

... for the first time on a turn or starts its turn there ...

It can take damage once per turn - there are as many turns in a round as there are creatures in a combat (excluding unintelligent mounts). Therefore it can take damage on its own turn if it starts or moves into in the AoE and on every other creature’s turn if it can be moved into the AoE (which may require moving it out first).

Answer 2

The wording is confusing. The spell says "for the first time on a turn", but since there are as many turns as there are creatures in the fight, several creatures could push the target in and out of the area of effect in their respective turn, thus making the target suffering the effects of the spell many times per round.

However, I don't think that was the intent of the rule, and the article provided by Zaphkiel explicitly sanctions that you can only make damage once per turn - meaning once per round. If that's the case, I'd rule that the "or" in

... for the first time on a turn or starts its turn there ...

is exclusive: it either suffers damage at the start of its own turn in the round, if it's already in the area of efect of the spell, or it suffers damage when it enters the area of efect of the spell as a result of its own actions in its turn, or the actions of others on their turns. In any case, only one damage per round.

The moonbeam spell is probably one of the worst worded in the rules, and it's not the first time this discussion arises: see here, and look for wyldwyzyrd's answer, for example.

Answer 3

The answer is provided in the article http://dnd.wizards.com/articles/features/rules-answers-april-2016

Reading the description of any of those spells, you might wonder whether a creature is considered to be entering the spell’s area of effect if the area is created on the creature’s space. And if the area of effect can be moved—as the beam of moonbeam can—does moving it into a creature’s space count as the creature entering the area? Our design intent for such spells is this: a creature enters the area of effect when the creature passes into it. Creating the area of effect on the creature or moving it onto the creature doesn’t count. If the creature is still in the area at the start of its turn, it is subjected to the area’s effect. Entering such an area of effect needn’t be voluntary, unless a spell says otherwise. You can, therefore, hurl a creature into the area with a spell like thunderwave. We consider that clever play, not an imbalance, so hurl away! Keep in mind, however, that a creature is subjected to such an area of effect only the first time it enters the area on a turn. You can’t move a creature in and out of it to damage it over and over again on the same turn. In summary, a spell like moonbeam affects a creature when the creature passes into the spell’s area of effect and when the creature starts its turn there. You’re essentially creating a hazard on the battlefield.

Since they use the word "and" instead of "or", it seems to imply a creature is damaged once each round, even if it starts its turn there.Think of it as the creature has already suffered the effect for that round (since it starts its turn in the same round).