Is "this damage cannot be reduced of prevented in any way" a catch-all, or is "reduced or prevented" referring to specific game mechanics?

Question

There are a number of spells that deal non-preventable damage. Wish, for example, states:

The stress of casting this spell to produce any effect other than duplicating another spell weakens you. After enduring that stress, each time you cast a spell until you finish a long rest, you take 1d10 necrotic damage per level of that spell. This damage can't be reduced or prevented in any way.

However, this non-preventable damage is worded as "This damage can't be reduced or prevented in any way". Damage reduction and damage prevention are AFAIK both specific mechanics that are more or less standardized, with spells, feats and equipment that grant these effects explicitly using these words.

It feels to me like non-preventable damage only stops effects that are explicitly worded as "reduces damage taken" or "prevent all damage taken", and that effects that use other words to affect the damage taken by the player may actually be able to stop the damage. For example, AFAIK D&D 5E has both damage reduction and damage resistance. However, I don't know if this is a correct interpretation.

So the question I have is: does "reduced or prevented" in this case explicitly refer to effects worded using the words "reduces damage taken" or "prevent all damage taken", or do they also refer to other effects that reduce or prevent damage with other words?

Answer 1

You’re describing a particular way of writing (and reading) rules: using keywords that allow rules to unambiguously indicate how they interact and interlock.

Most traditional RPGs aren’t written that way. Most are written as plain instruction manuals that don’t use a keywording structure for the rules. A number of non-traditional RPGs use keywords (Dungeon World is a prominent example), but most traditional RPGs don’t. A prominent exception is D&D 4e, which makes heavy use of keywording to define its rules. Outside of RPGs, the best example of keywording is also a WotC game: Magic the Gathering, which functions on a rigid structure of numbered rules and defined keywords that allow the card texts to be short yet rules-precise.

D&D 5e is traditional in its rules text: it’s an instruction manual that does not make its rules interact through only keywords. During its design and playtest, WotC explicitly said that it was to be read in “natural language”—plain English. (A design decision made, it seemed, to distinguish it from how 4th edition’s interlocking keyword-based rules work.)

As such, there are no hidden significances in the words rules use: they have their plain meaning, only referring to precise rule constructs when that is the plain meaning too, rather than a meaning that requires a keywords-based interpretation.

For this particular rule, it means just what it says, no keywords involved: the damage can’t be prevented or reduced in any way or by any means.

(Personally, I’d make an exception for divine intervention. That, to me, clearly trumps the “normal” state of affairs described by the merely-mortal spells that use this wording. That’s another feature of plain English reading: it allows for sensible situations the plain reading didn’t anticipate.)

Answer 2

There Are No Secret Rules

See this answer to What is the source of the "spells do only what they say they do" rules interpretation principle? While the question is talking about spells, the answer is relevant for the whole game.

The rules are always parsed as normal English. "This damage cannot be reduced or prevented in any way" means exactly what it says. Use of the word "any" in "cannot ... in any way" makes it inviolable.

There is no way around it. There is no room for interpretation, no ambiguity for a ruling on*. If you think you've found a way around it, you haven't, because it says there is no way around it right there.

*_{A "house rule" is different from a DM ruling on an ambiguity. A house rule is effectively a modification to the existing text.}