Spell / Charm / Hexes / Curses

Spell Definitions

Every now and then somebody asks me for the difference between a spell, a charm and a hex. Within the Potter world, the boundaries are flexible, and I imagine that wizards may have their own ideas. Hermione-ish, however, I've always had a working theory:

Spell:

The generic term for a piece of magic.

Charm:

Does not fundamentally alter the properties of the subject of the spell, but adds, or changes, properties. Turning a teacup into a rat would be a spell, whereas making a teacup dance would be a charm. The grey area comes with things like 'Stunning Spells', which on balance I think are Charms, but which I call spells for alliterative effect.

Hexes/ Jinx

Has a connotation of dark magic, as do jinxes, but of a minor sort. I see 'hex' as slightly worse. I usually use 'jinx' for spells whose effects are irritating but amusing.

Curses:

Reserved for the worst kinds of dark magic

http://harrypotter.wikia.com/wiki/Spell

Classification

Below is a list of all known categories that spells can be assigned to. It should be noted that the extent to which the following categories are mutually exclusive to each other is not known; i.e. whilst a spell can't be both a charm and a transfiguration it isn't known if a jinx could also be classed as a charm. It also seems likely that certain spell types belong to separate classification schemes to others. For example: Petrification is dark magic of the most advanced kind but it is also Transfiguration, Melofors is both a Jinx and a Conjuration, Fiendfyre could be considered a Charm as well as a curse and many healing spells could also be considered either charms or transfigurations. Hence, it appears that charm vs. transfiguration is one method of classification and counter-spell vs. jinx/hex/curse vs. healing spell a different one.

Spell Type	Defining Feature	Notes	Example
Transfiguration	Alteration of the object's form or appearance	Spells of this group may be separated into true transfiguration spells (where an existing object is altered) and conjurations, where the desired object is seemingly transfigured out of thin air.	Vera Verto - a true transfiguration spell that changes animals into water goblets.
			Avis - a conjuration that produces a flock of birds.
Charm	Alteration of the objects inherent qualities i.e. its behaviour and capabilities.	When cast by an experienced practitioner, charms appear to usually have fairly long-lasting effects.	Expelliarmus - the Disarming Charm, so-called because it changes its object's (the opponent's) quality from armed to disarmed by separating them from their wand.
Jinx	Minor dark magic; spells whose effects are irritating but amusing, almost playful and of minor inconvenience to the target.	Jinxes can only be maintained as long as the caster keeps eye contact.[2]	Impedimenta - the Impediment Jinx, which (appropriately) impedes the forward motion of an object.
Hex	Consistently affects the object in a negative manner; has a connotation of dark magic, but more so than a jinx. Major inconvenience to the target.		Anteoculatia - a hex that causes antlers to sprout from the object's head.
Curse	The worst kind of dark magic, intended to affect the target in a strongly negative manner.		Avada Kedavra - a.k.a. the Killing Curse, which kills the victim.
Counter-spell	Inhibition of the effect of another spell.	Counter-spells are a mysterious spell type that is not elaborated on very much throughout the franchise. There are six known types: Counter-jinxes, counter-curses, counter-charms, untransfigurations, anti-jinxes and undifferentiated counter-spells (it is unknown whether or not counter-hexes exist, though they presumably do). Whilst nomenclature is complex they all share the common trait of inhibiting another spell.	Finite Incantatem - a widely-employed counter-spell that terminates spell effects in general.
Healing spell	Improves the condition of the living object.		Episkey - heals minor injuries

A simplified analogy for the differentiation between a transfiguration and a charm is the difference between form and function or matter and energy; one is concerned with what the object is (its form - transfigurations) whilst the other is concerned with what the object is doing (its function - charms).