Camp Half-Blood the training ground for Greek demigods, located in Long Island, New York

Camp Jupiter the training ground for Roman demigods, located in California, between the Oakland Hills and the Berkeley Hills

Celestial bronze a powerful magical metal used to create weapons wielded by Greek gods and their demigod children

centurion an officer in the Roman army

charmspeak a rare type of hypnotism power that chosen children of Aphrodite possess

Cicero a Roman statesman who was renowned for his public speeches

Circus Maximus a stadium designed for horse and chariot racing

cloaca maxima Latin for greatest sewer

clunis Latin for buttocks

cohort groups of legionnaires

Colosseum an elliptical amphitheater built for gladiator fights, monster simulations, and mock naval battles

Commodus Lucius Aurelius Commodus was the son of Roman Emperor Marcus Aurelius; he became co-emperor when he was sixteen and emperor at eighteen, when his father died; he ruled from 177 to 192 CE and was megalomaniacal and corrupt; he considered himself the New Hercules and enjoyed killing animals and fighting gladiators at the Colosseum

Cumaean Sibyl an Oracle of Apollo from Cumae who collected her prophetic instructions for averting disaster in nine volumes but destroyed six of them when trying to sell them to Tarquinius Superbus of Rome

Cyclops (Cyclopes, pl.) a member of a primordial race of giants, each with a single eye in the middle of his or her forehead

cynocephalus (cynocephali, pl.) a being with a human body and a dog’s head

Dante an Italian poet of the late Middle Ages who invented terza rima; author of The Divine Comedy, among other works

Daphne a beautiful naiad who attracted Apollo’s attention; she transformed into a laurel tree in order to escape him

decimation the ancient Roman punishment for bad legions in which every tenth soldier was killed whether they were guilty or innocent

Delos a Greek island in the Aegean Sea near Mykonos; birthplace of Apollo

Demeter the Greek goddess of agriculture; a daughter of the Titans Rhea and Kronos. Roman form: Ceres

denarius (denarii, pl.) a unit of Roman currency

Diana the Roman goddess of the hunt and the moon; the daughter of Jupiter and Leto, and the twin of Apollo. Greek form: Artemis

Dionysus Greek god of wine and revelry; the son of Zeus. Roman form: Bacchus

dryad a spirit (usually female) associated with a certain tree

Eagle of the Twelfth the standard of Camp Jupiter, a gold icon of an eagle on top of a pole, symbolizing the god Jupiter

Earthborn a race of six-armed giants, also called Gegenes

Elysium the paradise to which Greek heroes are sent when the gods grant them immortality

Erythraean Sibyl a prophetess who presided over Apollo’s Oracle at Erythrae in Ionia

eurynomos (eurynomoi, pl.) a corpse-eating ghoul that lives in the Underworld and is controlled by Hades; the slightest cut from their claws causes a wasting disease in mortals, and when their victims die, they rise again as vrykolakai, or zombies. If a eurynomos manages to devour the flesh of a corpse down to the bones, the skeleton will become a fierce undead warrior, many of whom serve as Hades’s elite palace guards.

Euterpe the Greek goddess of lyric poetry; one of the Nine Muses; daughter of Zeus and Mnemosyne

fasces a ceremonial ax wrapped in a bundle of thick wooden rods with its crescent-shaped blade projecting outward; the ultimate symbol of authority in ancient Rome; origin of the word fascism

Fates three female personifications of destiny. They control the thread of life for every living thing from birth to death.

faun a Roman forest god, part goat and part man

Faunus the Roman god of the Wild. Greek form: Pan

Field of Mars part battlefield, part party zone, the place where drills and war games are held at Camp Jupiter

First Titan War also known as the Titanomachy, the eleven-year conflict between the Titans from Mount Othrys and the younger gods, whose future home would be Mount Olympus

Forum the center of life in New Rome; a plaza with statues and fountains that is lined with shops and nighttime entertainment venues

fuerte Spanish for strong

fulminata armed with lightning; a Roman legion under Julius Caesar whose emblem was a lightning bolt (fulmen)

Gaea the Greek earth goddess; wife of Ouranos; mother of the Titans, giants, Cyclopes, and other monsters

Gamelion the seventh month of the Attic or Athenian calendar that was used in Attica, Greece, at one time; roughly equivalent to January/February on the Gregorian calendar

Germani bodyguards for the Roman Empire from the Gaulish and Germanic tribes

Greek fire a magical, highly explosive, viscous green liquid used as a weapon; one of the most dangerous substances on earth

Grove of Dodona the site of the oldest Greek Oracle, second only to Delphi in importance; the rustling of trees in the grove provided answers to priests and priestesses who journeyed to the site. The grove is located in Camp Half-Blood Forest and accessible only through the myrmekes’ lair.

Hades the Greek god of death and riches; ruler of the Underworld. Roman form: Pluto

Harpocrates the Ptolemaic god of silence and secrets, a Greek adaptation of Harpa-Khruti, Horus the Child, who was often depicted in art and statuary with his finger held up to his lips, a gesture symbolizing childhood

harpy a winged female creature that snatches things

Hecate the goddess of magic and crossroads

Hector a Trojan champion who was ultimately slain by the Greek warrior Achilles and then dragged by the heels behind Achilles’s chariot

Helios the Titan god of the sun; son of the Titan Hyperion and the Titaness Theia

Hephaestus the Greek god of fire, including volcanic, and of crafts and blacksmithing; the son of Zeus and Hera, and married to Aphrodite. Roman form: Vulcan

Hera the Greek goddess of marriage; Zeus’s wife and sister; Apollo’s stepmother. Roman form: Juno

Hermes the Greek god of travelers; guide to spirits of the dead; god of communication. Roman form: Mercury.

hippocampus a sea creature with a horse’s head and a fish’s body

Horatius Cocles a Roman officer who, according to legend, single-handedly defended the Sublician Bridge over the Tiber River from the invading Etruscan army

Hyacinthus a Greek hero and Apollo’s lover, who died while trying to impress Apollo with his discus skills

immortuos Latin for undead

Imperial gold a rare metal deadly to monsters, consecrated at the Pantheon; its existence was a closely guarded secret of the emperors

Iris Greek goddess of the rainbow

jiangshi Chinese for zombie

Julius Caesar a Roman politician and general whose military accomplishments extended Rome’s territory and ultimately led to a civil war that enabled him to assume control of the government in 49 BCE. He was declared “dictator for life” and went on to institute social reforms that angered some powerful Romans. A group of senators conspired against him and assassinated him on March 15, 44 BCE.

Juno the Roman goddess of marriage; Jupiter’s wife and sister; Apollo’s stepmother. Greek form: Hera

Jupiter the Roman god of the sky and king of the gods. Greek form: Zeus

Jupiter Optimus Maximus Latin for Jupiter, the best and greatest god

Khromanda (Khromandae, pl.) a humanoid monster with gray eyes, a shaggy blond pelt, and doglike teeth; it can only communicate in loud shrieks

Koronis daughter of a king; one of Apollo’s girlfriends, who fell in love with another man. A white raven Apollo had left to guard her informed him of the affair. Apollo was so angry at the raven for failing to peck out the man’s eyes that he cursed the bird, scorching its feathers. Apollo sent his sister, Artemis, to kill Koronis, because he couldn’t bring himself to do it.