Gargoyle - a water spout terminating in a grotesquely carved figure of an animal or a human, used to direct water away from building walls. The word is from old French, gargouille, meaning throat (gargle), and it is also a dragon from France. If it isn't a waterspout, it's called a "grotesque".

Geloscopy - a form of Divination predicting futures from laughter

Geomancy - Divination where a handful of loose dirt is cupped between the hands and tossed to the ground. Its patterns are then interpreted. A later form, called paper geomancy, has the diviner ask a question and, with eyes closed, tap the point of a pencil onto a sheet of paper, making several random marks until he feels like stopping. The resulting patterns are interpreted.

Ghost - the disembodied soul of a dead person, present in the stories of almost every civilization. Ghosts appear in many forms. The most basic, universal type is the apparition, or disembodied spirit. Some seem to be a pale mistlike vapor, but others resemble normal, flesh-and-blood humans. Europe abounds with stories of human-looking ghosts, who eat, drink, and carry out most of the functions of living people. The ghostly nature of these specters is revealed only when they vanish into thin air, or by the odd musty/rotting odor some ghosts leave behind like the perfume of the dead.

Ghoul - the evil ghost or spirit, according to muggles, who believe they dig up corpses and eat rotting human flesh. Ghouls originated in ancient legends of Arabian Muslims, known as ghul, a spirit both evil and rebellious. Wizards, however, understand that though ghouls are slimy, buck-toothed and unattractive, they're relatively harmless. They live in the attics or barns of wizards, and live off spiders and moths.

The chameleon ghoul is known to change into something fittng its environment. A good example of this happens to be suits of armour in Hogwarts' castle setting which aren't truly what they appear to be.

Giant - beings of superhuman size and strength, most often assumed to be cruel and ruthless, have important roles in the creation myths of many cultures. Often, they existed before the gods did.

Greek mythology gives us the Titans, creatures as tall as mountains and unbelievably strong, born when the blood of the Heavens (or Uranus) showered Gaea (aka the earth). They were hideous, with scaly feet, hirsute faces, and sometimes, with multiple heads. The Titans fought the gods of Mount Olympus in a war so violent it almost destroyed the universe. It took Hercules, the mortal son of Zeus, to help defeat the Titans, who were buried inside of mountains that became volcanoes.

During the Middle Ages, the lore of giants continued to make them bloodthirsty, violent, and cannibalistic. They ranked with dragons as worthy opponents for the noble, chivalrous knight, who would defeat these avaricious and gluttonous beings.

The race of giants live in remote mountain regions now. Once they allied themselves with Voldemort, and take the blame for many of the worst incidents of murder and torture which occured then. Aurors killed many of the giants. Those who survived, fled. Hagrid's father was a "normal" person but his mother was the giantess, Fridwolfa. The headmistress of Beauxbatons is also part giant.

Gillyweed (Plant) - a water plant native to the Mediterranean, resembling a cluster of slimey, grey-green rat tails. Gillyweed must be eaten to produce its effect of giving someone gills, webbed feet and hands for about an hour's time.

Ginger (Plant) - ginger roots are one of the ingredients of Wit-Sharpening Potion.

Glumbumble - a flying gray insect with a furry body from northern Europe. It feeds on nettles and makes a treacle that induces melancholy. Glumbumbles nest in dark seclusion in tree hollows and caves.

Gnome - as far as muggles know, a gnome is: Either a creature of legend, resembling a tiny old man who lives in the depths of the earth and guards buried treasure; or he's a scuplture of a bearded little man in colorful clothes and wearing pointy red hats, decorating the garden.

To wizards, however, gnomes are garden pests that look a lot like potatoes on legs. They live underground, digging up roots and causing a general mess.

Goblin - the folklore of medieval England portrayed goblins as helpful, yet tempermental, imps or household spirits. Varying in size, most seem to be about half the height of an adult human. They usually have gray hair and beards, and their bodies and/or faces tend to be distorted in some grotesque fashion. They could possess too many fingers or toes, have no ears, own wrongside-down eyelids, limbs without joints, or speak in strange voices with lisps or in a high pitch. They are undeniably clever, however, as they are the guardians for Gringott's Bank.

Granian (Winged Horse) - a fast, gray horse

Graphorn - lives in mountainous areas of Europe. A humpback creature that has two long, sharp horns. It is large and greyish purple in color. It has large, four-thumbed feet. Its nature is very aggressive, making the acquisition of its horns (powdered form used in several potions) and hide (tougher than a dragon's hide, repellent to most spells) difficult.

Griffin - originating in India, a griffin is a magical creature with the front body of an eagle and the hind end of a lion. They were used to guard gold. A muggle belief claims that people can't lie when they find themselves in the company of a griffin.

Medieval griffin with prey

Grim (Barghest) - the ghostly apparition of a large, dog-like beast with fiery eyes, and a guardian of dead souls. Seeing one portends death.

Grimoire - see Magic: Grimoire - translated as "black book", a book of spells and incantations to conjure up spirits and demons

Grindylow - a water demon that lives in weed beds in lake bottoms in Britain. The Grindylow is pale green. It has long, brittle fingers with which to grip its prey (it prefers children; adults are possibly too strong for it to harm), sharp little horns, and green teeth. They live in the lake near Hogwarts.

Gryffindor - one of the four houses of Hogwarts School of Witchcraft and Wizardry.

Gryffindor, Godric - founder of Gryffindor House

Gubraithian Fire - everlasting fire created by a spell that can't be performed by just any wizard

Gurg - a title that means "Chief of the Giants"