SPELLS DICTIONARY-R
Makes something smaller. Mad-Eye Moody uses it in GoF. Countercharm to Engorgio. (Whether or not Reducio can also be used by itself, rather than countering Engorgio is unknown. If possible it would shrink normal sized items into minature versions of themselves. References in CoS by Arthur Weasley to "shrinking doorkeys" would make this seem likely.)
By casting this curse one is able to disintegrate objects in one's path. It is possible to increase the spell's power, meaning that if you had enough magic support behind it, it could wreak incredible devastation. (In GoF, Harry uses it on one of the hedges of the Triwizard maze, and ends up burning a small hole in it; in Harry Potter and the Order of the Phoenix, Parvati Patil is referenced as being able to reduce a table full of dark detectors to ashes; thus, it must be possible to perform the curse with different levels of power.)
Charm probably used to release amounts of force. In Latin relatio means a giving back and relaxo means I loosen. Used by Harry Potter against Grindylows in the second task of the Triwizard Tournament, above ground it ejects sparks from the wand, below water it ejects boiling water from the wand. When used more expertly by Auror Bob Ogden in Chapter 10 of Harry Potter and the Half-Blood Prince, Marvolo Gaunt is thrown backwards.
This spell appears to rouse an unconscious person. Used by Harry in Harry Potter and the Half-Blood Prince. Possibly a cosmetic variation of Ennervate.
Used to repair objects. Used countless times throughout the books. First seen in the 1st book, used by Hermione Granger to fix Harry's glasses, as "oculus reparo".
Tickling Charm. The incantation comes from the Latin words risus ("laughter" or "ridule") and semper ("always") - "laughter always". Harry uses it on Malfoy in CoS in the duelling club. The spell has different effects in other media.
In the Chamber of Secrets movie, Harry used this spell to fling Malfoy through the air and in the game Rictusempra is used to stun people or animals.
A spell used when fighting a Boggart, "Riddikulus" forces the Boggart to take the appearance of what the spellcaster is thinking as amusing so that the laughter will weaken it. First seen in PoA, the Latin word "riddiculus" means "exciting laughter", "laughable", or simply "laughter". It is pronounced with a hard "c".
