Is a ghast a type of spirit, or it is a palette-swapped ghoul?

>>50376536
It is a type of vampire.

>>50376536
The name probably originates from the adjective "Ghastly"
>from Old English gæstan "to torment, frighten" (see ghost (n.)). Spelling with gh- developed 16c. from confusion with ghost. Middle English also had gastful in the same sense, but this is now obsolete. Sidney and Shakespeare also used ghastly as an adverb. Related: Ghastliness.

The first modern instance of "Ghast" used as a name for a monstrous creature came from Lovecraft. Ghasts were predatory creatures of the Dreamlands with something akin to kangaroos if I remember correctly.
They were then taken as monsters and upgraded versions of Ghouls in D&D and spread from there.
The association with ghouls comes from the fact that the scene in which they are described in The Dream-Quest of Unknown Kadath features ghouls as well, and ghasts are described as predators for ghouls.

>>50376621
In other words:
The source from which 'ghast' as a type of creature has been spread out and became popular is D&D, which presented it as a stronger ghoul - aka a cannibalistic, cursed humanoid with a paralyzing touch.

The source from which it was taken from D&D was Lovecraft who had them as large, eerie predators with some humanoid traits and other monstrous; aside from their look they were 'mundane' creatures, although they inhabited the dreamlands/the dimensions beyond.

These are the only milestones you may have as a source. Most people nowadays are used to connect ghasts with undeath, or at least with morbid themes and graveyard settings, because of D&D.

>I demand a single objectively correct answer!
The correct answer within the given parameters is objectively wrong.

>>50376536
>it most definitely does not depend on the setting.
Except that it does. I would tend to agree that "ghoul" now has a commonly accepted meaning (debatably-undead eater of dead bodies) and that if ghasts are palette-swapped ghouls, they can't also be a type of spirit. However, there's nothing saying that they have to be either.

In other words, the correct answer to your question is, to use the Japanese, "mu", or "your question is incorrect".