SPELLS DICTIONARY-E
Makes something grow larger. Seen in GoF when the impostor Professor Moody casts it on a spider to enhance a demonstration of the effects of a Cruciatus Curse. Hagrid is also suspected of performing the charm on his pumpkins once.
The counterspell to the Stunning Spell. In GoF, Amos Diggory uses it to wake up Winky, while later on Professor Dumbledore uses it to wake up Viktor Krum. In Harry Potter and the Half-Blood Prince, Harry uses it in an attempt to wake Professor Dumbledore. Maybe more than a counterspell, there have been instances when it is used to help people regain consciousness who haven't been Stupefied. The etymological root of this spell is from Latin for "to add nerve"; hence the English word "ennervate". If spelled with one "n," however, it has the opposite meaning - to weaken, rather than invigorate (though a post hoc explanation could be fashioned to claim that it is the stunning spell that is weakened by this spell, in which case the etymology would fit).
Used in GoF after the first task of the Triwizard Tournament. Nymphadora Tonks uses this spell in Harry Potter and the Half-Blood Prince to fix Harry's broken nose, later Harry uses it to heal a fat lip. This leads the reader to the conclusion that it is a spell to heal minor injuries (assuming you consider a broken nose a mild injury). The word comes from the Greek "episkevi", which means "repair". J. K. Rowling writes in Harry Potter and the Half-Blood Prince, Harry's knowledge tells him that this spell could belong to a family (or variety) of Healing Spells, in the same way a species of plants belongs to a larger genus.
Makes something vanish. Used in OotP when Snape makes Harry's Draught of Peace disappear from his cauldron. Also used in CoS when Snape makes the snake disappear. In OotP, this spell is used to make Bill's scrolls on the kitchen table vanish. It is presumed that whatever is Vanished can be made to reappear - surely Bill didn't want his scrolls to disappear completely, never finding them again.
This spell conjures a Patronus, a silvery phantom shape, usually that of an animal, which is the embodiment of the positive thoughts or character/personality/desire of the caster. A Patronus will drive away Dementors and Lethifolds. A patronus "is an anti-Dark device, which makes it highly resilient to Dark wizards; it is not hindered by physical barriers; each Patronus is unique and distinctive; nobody else can conjure another person's Patronus." Harry conjures a stag as his Patronus, while Hermione Granger conjures an otter, Ron Weasley summons a Jack Russell Terrier, and Cho Chang a swan; but, a Patronus can change form when someone has undergone emotional turmoil (as character/personality of the caster may change as well).
In order for the spell to work, the person must concentrate on a happy memory, which is especially difficult in the presence of a Dementor. Latin "expecto patronum" means "I expect (welcome is the literal translation) a guardian," although the Latin phrase is deep in ambiguity: ex + pecto would mean from the chest (prehaps "from the heart", implying that the Patronus is the heart's guardian), and patronum is an archaic word for father, implying that another interpretation is "I expect my father.", which could be related to the fact that Harry's patronus takes his father's animagus form. If the thought is not focused on strongly enough, a silver glow or mist appears, which does little but slow down a Dementor for a moment. Members of the Order of the Phoenix are taught by Dumbledore how to send messages through their Patronuses, and they are the only ones in the world who know this special technique, as it is Dumbledore who came up with this ingenious idea.
The disarming spell. This spell is used to disarm another wizard, typically by causing the victim's wand to fly out of reach. It also throws the wizard backwards a few feet when enough power is placed behind it. As demonstrated in the novel PoA, simultaneous use of this spell by multiple people on a single wizard can throw the wizard back more powerfully. First seen in CoS, when Snape disarms Lockhart in the Duelling Club. Also used in HBP, when Draco Malfoy disarms Dumbledore.
When dueling in the CoS video game, Expelliarmus can be used as a shield, much like the Protego charm. In the PoA video game, if aimed at the wand's owner it can make their spell backfire. This spell is also used in GoF when a giant spider is holding Cedric Diggory, Harry uses it so that Cedric is free.
Etymology: likely a combination of "expel" and "arm" (when "arm" means "weapon")
