Monks use "ki," barbarians use "rage" and spellcasters can use "spells": how do you classify these systems? Is their a term that defines these types of systems? Their not class unique (Spells).

I can't figure out what their called: when I try to think of a name for them, I think "their point systems and they allow the user to use abilities like teleport or all kinds of things, so why not call them 'ability points'." But of course "ability points," already have another meaning, so what do you call these? How about "Special mechanics systems" or "consumable mechanics?"

I don't know if there is a specific term for them, but I just think of them as "Class Feature Resource Trackers".

Spellcasting is a system in its own right, and it's pervasive and iconic enough to be considered separately from class-specific resources IMO. So I call them "spells" and "(sub)class features."

But if you're looking for some unified theory behind all PC resources, I don't think you'll find it. 5e was not designed to be a fresh system built from the ground up - 4e did that and it was not received well. Many aspects of 5e are translations or fusions of old systems and then they adjusted things here and there when it seemed necessary.

5e is not remotely coherent enough as a design for everything in it to have the same unifying mechanical structure.  This is both good and bad; it means the game is harder to grasp and has more mechanical overhead, which some people absolutely hate, but it also means classes are allowed to explore the mechanics that work best for their own specific requirements.

Spellcasting is its own thing.  You could think of the rest as 'Class Resources', but that paints an over-broad and incomplete picture.  I'd simply not worry about it.

Quote from Yurei1453 >>

5e is not remotely coherent enough as a design for everything in it to have the same unifying mechanical structure.  This is both good and bad; it means the game is harder to grasp and has more mechanical overhead, which some people absolutely hate, but it also means classes are allowed to explore the mechanics that work best for their own specific requirements.

Spellcasting is its own thing.  You could think of the rest as 'Class Resources', but that paints an over-broad and incomplete picture.  I'd simply not worry about it.

 I'm fine with their being a "non-unifying mechanical system," if their was one, then classes would have less diversity. What I'm looking for is a term that defines spells, ki, rage, etc. as category of "actions"

 That term, as best as 5e would allow, is 'Class Resource' or "Class Mechanic'.  A unifying term requires there to be a unifying theme or throughline, and there really isn't one.  Each class functions fundamentally differently, with only a few exceptions outside of spellcasting being exactly, perfectly, infuriatingly identical for every last single spellcaster in 5e.

If you want a term that is similar to "Ability", but not already claimed by 5e game terms, Thesaurus.com points toward the following: "Talent", "Knack", or "Gift".

Quote from Yurei1453 >>

This is both good and bad; it means the game is harder to grasp and has more mechanical overhead, which some people absolutely hate

 I think this is the first time I've ever heard someone suggest 5e has too much mechanical overhead.

Quote from Squiggit >>

Quote from Yurei1453 >>

This is both good and bad; it means the game is harder to grasp and has more mechanical overhead, which some people absolutely hate

 I think this is the first time I've ever heard someone suggest 5e has too much mechanical overhead.

 Any class-based system has some bloat in that department - classes themselves are unnecessary overhead. It wouldn't be D&D if it were classless though.

I added a poll to the top of the discussion, thoughts?

"Class Feature" might be the term you're looking for, as unsatisfactory as that feels. That's the header which all of a Monk or Barbarian's.... stuff falls under. But, some stuff does end up under the "class feature" header which also feels like it shouldn't be there... your starting equipment is a class feature? I guess so, even if you don't have it on you any more!

If you're describing actions, you can perhaps talk about four five? types:

1. 'General Actions'? 'Standard Actions'?: "one of the actions available to all creatures... as described in the Player’s Handbook." That language (or minor riffs on it) is pulled from various places in PHB, DMG, and MM, and is in reference to PHB Chapter 9 Actions in Combat. 
2. 'Improvised Actions': "an action that you improvise" which "the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure." There are not many rules on that apart from those two sentences, but there's also a short sidebar below Use an Object in PHB Chapter 9, which in turn refers you to PHB Chapter 7 to help identify relevant skill and ability score modifiers for improvised novel actions.. 
3. 'Monster/NPC Statblock Actions': "Many monsters have action options of their own in their stat blocks." (or similar language in the DMG). This is anything like Maul or Devour Brain or whatever, and will be a self-contained action which describes its own modifiers.
4. And finally, 'Special Actions' derived from your class, race, equipment, or active spell effects: "an action you gained from your class or a special feature," which covers everything else. You could optionally subdivide that as class actions vs. racial actions vs. equipment actions etc.... but why bother, when they all work the same? 'actions you find on your character sheet, or in the text of an active spell effect on you'... okay, maybe "Spell Effect Actions" kind of deserves to be its own section, since the rules for it won't be found on your character sheet so much as in the spell description, so...
5. Spell Effect Actions , see 4 above. 

Bolded names for these I just came up with on the fly, but I think most folks would understand what you're getting at if you called Rage a "special action, derived from a Class Feature."

Oh, and "class resource" is a far more elegant term than any of the ones on your poll, and a lot of people already use that :) 

You'd be surprised, Squig.  There's a lot of rulesets out there with vastly less mechanical complexity than 5e, systems whose entire rulebooks clock in under fifty pages.  Many of them designed to try and entice people who've never played a game in their life, 'TTRP' or otherwise, for whom 5e's character design system is a Labyrinthian nightmare of alien geometries.

'Course, I've maintained for a while now that reducing complexity is not how you attract these folks.  It's not an issue of complexity - these people are not necessarily stupid or incapable of comprehending complex* systems, it's an issue of teaching people a new language.  These are folks that do not speak Gamer, that do not think in Gamer.  They don't make the same connections we do, they don't have the same assumptions and familiarities we do.  Once you teach someone the language, get them speaking the same Parseltongue the rest of us do?  Complexity is no longer an issue, and all the other shitty compromises those Rules-Ultralite systems have to make to fit their entire system inside fifty pages become quickly apparent.

But I suppose that's probably a discussion for a different thread, fascinating as I find the subject myself.

 I think "resource pool" will be the term I use to describe these systems, at least for now, I'm partially satisfied with the results of this discussion thread. Thank you everyone for your input.

Quote from Chicken_Champ >>

"Class Feature" might be the term you're looking for, as unsatisfactory as that feels. That's the header which all of a Monk or Barbarian's.... stuff falls under. But, some stuff does end up under the "class feature" header which also feels like it shouldn't be there... your starting equipment is a class feature? I guess so, even if you don't have it on you any more!

If you're describing actions, you can perhaps talk about four five? types:

1. 'General Actions'? 'Standard Actions'?: "one of the actions available to all creatures... as described in the Player’s Handbook." That language (or minor riffs on it) is pulled from various places in PHB, DMG, and MM, and is in reference to PHB Chapter 9 Actions in Combat. 
2. 'Improvised Actions': "an action that you improvise" which "the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure." There are not many rules on that apart from those two sentences, but there's also a short sidebar below Use an Object in PHB Chapter 9, which in turn refers you to PHB Chapter 7 to help identify relevant skill and ability score modifiers for improvised novel actions.. 
3. 'Monster/NPC Statblock Actions': "Many monsters have action options of their own in their stat blocks." (or similar language in the DMG). This is anything like Maul or Devour Brain or whatever, and will be a self-contained action which describes its own modifiers.
4. And finally, 'Special Actions' derived from your class, race, equipment, or active spell effects: "an action you gained from your class or a special feature," which covers everything else. You could optionally subdivide that as class actions vs. racial actions vs. equipment actions etc.... but why bother, when they all work the same? 'actions you find on your character sheet, or in the text of an active spell effect on you'... okay, maybe "Spell Effect Actions" kind of deserves to be its own section, since the rules for it won't be found on your character sheet so much as in the spell description, so...
5. Spell Effect Actions , see 4 above. 

Bolded names for these I just came up with on the fly, but I think most folks would understand what you're getting at if you called Rage a "special action, derived from a Class Feature."

Quote from Yurei1453 >>

 That term, as best as 5e would allow, is 'Class Resource' or "Class Mechanic'.  A unifying term requires there to be a unifying theme or throughline, and there really isn't one.  Each class functions fundamentally differently, with only a few exceptions outside of spellcasting being exactly, perfectly, infuriatingly identical for every last single spellcaster in 5e.