"Nox" — the anti-charm for Lumos, removing the light from your wand. Nox is the Latin word for "night" — making the spell rather self-explanatory. An incantation for "night" will take away the light from your wand. Harry was famous for disarming his enemies. Read more
Accio (Summoning Charm): A common charm used to summon an object (potentially over a large distance). In the Triwizard Tournament, Harry uses Accio to summon his Firebolt during the First Challenge.
The Wand-Lighting Charm (Lumos) was a charm that illuminated the tip of the caster's wand, allowing the caster to see in the dark. The counter-charm for the spell was the Wand-Extinguishing Charm (Nox), which was used to extinguish the light from the caster's wand.
The three Unforgivable Curses are the Cruciatus Curse, which causes unbearable pain; the Imperius Curse, which allows the user to control the actions of the victim; and the Killing Curse, which causes instant death.
Roughly translated, Expelliarmus – the Disarming Charm – means 'to drive out a weapon' and that's what it does: forces the subject to drop whatever they're holding.
Sister spells Lumos and Nox give light and take it away, respectively. Lumos could well come from the 19th-century Latin word 'lumen', which simply means 'light'. Adding the Latin suffix 'os' means to 'have something': to have light, in this instance. Nox is Latin for 'night', but is also rooted in Greek mythology.
Expecto Patronum, or the Patronus Charm, will cast a Patronus, which can appear as simply white vapour, or in more advanced casters, as a silvery-white animal shape. If it takes the shape of an animal, it is called a corporeal Patronus. This spell is used to ward off Dementors, which are the guardians of Azkaban.
Sectumsempra was a curse invented by Professor Severus Snape that lacerates the target and causes severe haemorrhaging. Snape created it as a student of Hogwarts, with the intention of using it against his enemies, likely including the Marauders, and it became one of his specialities.
The second-favorite spell of fans was Accio, which is simply used to summon something to you, which Harry famously used in the Triwizard Tournament to summon his broom.
Accio: Also known as the summoning charm, Accio summons any object to the user within a certain distance. In the Goblet of Fire Harry uses Accio to summon his broomstick during the first Triwizard Challenge.
The Banishing charm was the counter-charm to the Summoning Charm. As Accio summoned objects to the caster, Depulso send objects away. The Anti-theft Charm was placed on several magical objects of public or private property to prevent it from being summoned by anyone but the owners of said objects.
The Muffliato Charm (Muffliato) was a charm used to fill the ears of any person in the vicinity of the caster with an unidentifiable buzzing sound so as to allow for conversation without being overheard.
Bellatrix laughed, the same exhilarated laugh her cousin Sirius had given as he toppled backward through the veil, and suddenly Harry knew what was going to happen before it did. Molly's curse soared beneath Bellatrix's outstretched arm and hit her squarely in the chest, directly over her heart.
Before he released the Boggart, Lupin taught Harry the incantation, Expecto Patronum, and gave Harry a short lecture on the Patronus Charm and its effects.
In the the film adaptation of Harry Potter and the Order of the Phoenix, only Ginny casts the Reductor Curse to smash the shelves in the Hall of Prophecy, instead of every D.A. member present.
-nox-, root. -nox- comes from Latin, where it has the meaning "night. '' This meaning is found in such words as: equinox, noctambulism, nocturnal, nocturne.
Neville casts this spell. Riddikulus is a charm that is used in defence against a Boggart. It causes the creature to assume a form that is humorous to the caster, thereby counteracting the Boggart's ability to terrorise.
This charm extinguishing wand-light The Wand-Extinguishing Charm was invented by the same witch who invented the Wand-Lighting Charm, Levina Monkstanley.
He's simply a name dropped on Albus Dumbledore's chocolate frog card in "Harry Potter and the Sorcerer's Stone": "Dumbledore is particularly famous for his defeat of the Dark wizard Grindelwald in 1945."
Although it might not have killed Nagini, the killing curse did succeed in destroying the Horcrux side of Harry.
I suppose you are referring to all confrontations between Harry and Voldemort where somehow Harry is able to block the unblockable killing spell shot by Voldemort. Expelliarmus did not beat Avada Kedavra. Voldemort's wand (the elder wand) recognized its true master (that was Harry) and refused to attack it.