ABSOLUTE RECORD

A major information repository of the Forerunner ecumene, a vast archive where Forerunner technology was cataloged.

AC

Autocannon, a powerful human weapon employed on a variety of vehicles.

ACTIVATION INDEX

A device used to activate and fire a Halo ring.

ALPHA-NINE

Formal designation of the ODST (and later Spartan-IV) fireteam led by Edward Buck.

ANCESTORS

The name given to the prehistoric, spacefaring human civilization that maintained an empire outside Forerunner control.

ANCILLA

High-order Forerunner artificial intelligence developed over generations.

APFSDS

Armor-Piercing Fin-Stabilized Discarding Sabot, ammunition commonly used in human sniper rifles.

ARK

Forerunner factory and archive that constructed the Halo Array and housed samples of life preserved as part of the Conservation Measure.

ARMIGER

Forerunner combat machines utilized for ground operations, the most common being the soldier.

ARTIFICIAL INTELLIGENCE (AI)

Highly sophisticated software construct that displays many of the behavioral and functional characteristics associated with biological, thinking life.

ASGM

Automatic Self-Guided Missile, explosive rockets employed by humanity’s artillery, aircraft, and spacecraft.

ASSEMBLY FORGES

Covenant manufacturing facilities that build items piece-by-piece using clouds of programmable nanomachines.

ASW

Anti-Ship Weapon utilized by human spacecraft against enemy ships.

A/X

Atmospheric/Exoatmospheric, indicating flight capability both in atmosphere and in space.

BLOODSTARS

A special operations unit of the Covenant (later appropriated by the Banished) dedicated to the pursuit and killing of Spartans.

BRUTES

See JIRALHANAE.

BUILDER

Forerunner rate that designed and constructed machinery and artificial minds.

CAA

Colonial Administration Authority, the previous administrative body for humanity's colonies, established in 2310.

CHARUM HAKKOR

Capital world of the Ancestors, believed to have once been a Precursor hubworld due to its abundance of neural physics-based structures.

CMA

Colonial Military Administration, the now-defunct military and policing body for humanity’s colonies, established in 2310.

COMBAT SKIN

Forerunner battle armor and environmental suits worn under specialized carapaces.

ComL

Composition L, incendiary material used for human-made anti-infantry explosives.

COMPOSER

Forerunner neural physics device for transforming biological minds into digital essences.

CONSERVATION MEASURE

A Forerunner plan to preserve and reseed sentient life in the galaxy after the activation of Halo.

COVENANT

An alliance of species under the authority of San’Shyuum and Sangheili, unified in the belief that the Forerunners built Halo to transcend beyond biological life and enter a higher plane of existence.

COVENANT FRINGE

Civilizations that were not fully inducted into the Covenant, but were exploited for their strategic and infrastructural advantages.

COVENANT WAR

Human name for the genocidal conflict with the Covenant that started with the attack on Harvest in 2525 and ended with the Prophet of Truth’s death on the Ark in 2552.

CRYOTUBE

Cryogenic stasis unit used by humans on interstellar voyages to endure protracted travel times and to preserve medical patients.

CQB

Close-Quarters Battle, referencing weapons, armor, equipment, or strategies employed in close proximity to the enemy.

CQC

Close-Quarters Combat, referencing weapons, armor, equipment, or strategies employed in close proximity to the enemy.

DESIGN PATTERN

Instructions fed to nanomachines that construct Covenant machinery, often utilized for both weapons and vehicles.

DESIGN SEED

Construction templates for Forerunner machinery, fed to assemblers for mass replication.

DIDACT

The title given to the legendary Forerunner military commander (Ur-Didact) and the young Builder he imprinted who replaced him (IsoDidact).

DOISAC

Former homeworld of the Jiralhanae, destroyed by Cortana.

DOMAIN

An incredibly ancient, self-aware knowledge network used by the Forerunners to document, transmit, and interpret all information and personal memory in their galaxy-spanning realm.

DOMUS DIASPORA

The name given to humanity’s interstellar expansion and colonization period, beginning in 2362.

DRAGOON

First-order Forerunner capital ship used for initiating long-range strikes and raiding.

DREADNOUGHT

Covenant name for the Forerunner keyship used to power High Charity. Also, a prominent type of armored Banished warship.

DRONES

See YANME’E.

DROP POD

Small reentry vehicle used to transport combat troops from planetary orbit to the surface.

DROPSHIP

Transatmospheric vehicle deployed to deliver cargo and personnel to and from orbit.

EARTH

The homeworld and center of governance for contemporary, 26th century humankind.

ECUMENE

The worlds and realms of the galaxy occupied and controlled by the Forerunners during their time.

ECUMENE COUNCIL

Prime governing body of the Forerunners comprised of at least five hundred representatives from the various Forerunner rates and territories.

ELITES

See SANGHEILI.

ENDLESS

See XALANYN.

ENERGY SHIELDING

Network of generators that creates overlapping fields of invisible force that reflect, dissipate, or absorb attacks.

ENGINEERS

See HURAGOK.

ERDE-TYRENE

The common name for Earth during the time of the Forerunners.

ESSENCE

An archive of a mind, personality, and even being, utilized historically by the Forerunners in various ways.

EVA

Extra-Vehicular Activity, as in actions taking place typically in the context of space or other zero-gravity scenarios outside of a spacecraft.

EXCESSION

The name given by human researchers to the Forerunner portal complex uncovered on Earth that provided access to the Ark.

FERRET

A covert team of ONI special operatives led by Veta Lopis.

FLOOD

Voracious hive-mind parasite capable of seizing, converting, and controlling sentient hosts in an effort to perpetuate its kind.

FLOOD WAR

The Forerunners’ prodigious conflict against the Flood which ultimately engulfed the entire galaxy and ended with the destruction of their civilization.

FMJ-AP

Full Metal Jacket - Armor Piercing, ammunition used in human infantry rifles.

FORERUNNER

An ancient civilization of highly advanced beings believed to have perished during the activation of Halo many millennia ago.

FORERUNNER RATES

Physiological modifications and psychological peculiarities that defined the different Forerunner occupational and social castes.

FSC

Flood Super Cell, the basic cellular material that comprises Flood tissues and membranes.

FTP-HE

Ferric-Tungsten Projectile ‑ High-Explosive, powerful ammunition used in some exotic human weapons.

FUSION DRIVE

Human maneuver drive that utilizes a fusion reactor to superheat reaction mass (often water or hydrogen) and expel it at high velocities for sublight travel.

GAU

Gun, Aircraft Unit, a weapon implement used by human aircraft.

GAUSS CANNON

Semi-portable and vehicle-mounted electromagnetic launchers that typically fire hypervelocity armor-piercing projectiles.

GEAS

A method by which Lifeworkers adjusted species in their care through brain-pattern imprinting and subtle genetic commands for various ends. Also known as “genesong.”

GEN1

First Generation, referring to Mjolnir armor previously worn by Spartan-IIs and Spartan-IIIs.

GEN2

Second Generation, referring to Mjolnir armor generally worn by most Spartans immediately after the Covenant War, especially Spartan-IVs.

GEN3

Third Generation, referring to Mjolnir armor worn by nearly all contemporary Spartans as of 2560.

GLASSING

Covenant close-orbit and near-surface bombardment of military and urban sites with massed energy projectors to vitrify the world’s soil and decimate its habitability.

GRAVEMIND

Composite mind that controls and directs the Flood, the last vestige of the Primordial, growing in influence as the parasite expands its presence.

GREAT IMMOLATION

The brutal Jiralhanae civil war that left their homeworld on the edge of nuclear annihilation, shortly before their species joined the Covenant.

GREAT JOURNEY

Central religious belief held by the Covenant that the activation of Halo would elevate its members into the divine while scouring the galaxy clean of unbelievers.

GREAT SCHISM

Covenant civil war instigated in November 2552 when the High Prophet of Truth attempted to consolidate his power within the empire.

GRUNTS

See UNGGOY.

GUARDIAN

Machines employed by the Forerunners as tenders and recorders of the Precursors’ legacy, ultimately utilized as enforcement constructs to pacify and police other civilizations.

HALO ARRAY

Seven ringworld weapon installations that, upon activation, can kill all sapient life in the galaxy.

HE

High-Explosive, a descriptor of human ammunition that explodes upon impact.

HEI/AP

High-Explosive Incendiary/Armor-Piercing, ammunition used by human artillery.

HEI/RD

High-Explosive Incendiary/Remote Detonated, ammunition used by exotic human explosive launchers.

HIGH PROPHETS

The three highest-ranking San’Shyuum who led the Covenant, also known as hierarchs.

HMG

Heavy Machine Gun, a human infantry weapon.

HUD

Heads-Up Display, an arrangement of intel provided to UNSC personnel via their helmet’s visor.

HUNTERS

See LEKGOLO.

HURAGOK

Also known as Engineers, they are Forerunner biomechanical servant-tools with an innate ability to construct, repair, maintain, and augment advanced technology.

HV/FTHPP

High-Velocity/Ferric-Tungsten Hollow-Point Projectile, specialized ammunition typically used in Gauss cannons and mass drivers.

HVE

High-Velocity, Explosive, powerful ammunition used by human machine guns.

INNER COLONIES

Habitable worlds with the shortest travel time to Earth, colonies that were generally purpose-developed and affluent.

INSURRECTION

Broad term for the conflict defined by the hostile actions of rebels and malcontents who opposed Earth’s control of the colonies.

INVARIANT BIAS

The Contender-class ancilla that serves as the custodian of the Absolute Record.

JACKALS

See KIG-YAR.

JANJUR QOM

Former homeworld of the San’Shyuum, allegedly destroyed by its star going supernova.

JIRALHANAE

Also known as Brutes, a pseudo-ursine species with an aggressive nature, as well as impressive size and strength, that dominate the ranks of the Banished.

JOINT OCCUPATION ZONE

Regions of space held and settled by both the Unified Earth Government and other alien species.

KEYSHIPS

Forerunner transports commissioned to index and catalog much of the sentient life that remained in the galaxy during the final years of the Flood War.

KIG-YAR

Also known as Jackals and Skirmishers, a saurian-avian species that serves in scout, skirmisher, and marksman roles within the Banished.

KNIGHT

Promethean armiger controlled by the composed essence of a human or Forerunner warrior.

LAAG

Light Anti-Aircraft Gun, a powerful human weapon designed for use against enemy aircraft.

LEKGOLO

Gestalt intelligences comprised of eel-like organisms clustered together in colonies, and capable of assembling into a variety of forms. Often encountered as Hunters (Mgalekgolo).

LIBRARIAN

Forerunner referred to as the Lifeshaper, the greatest of the Lifeworkers and the architect of the Conservation Measure.

LIFEWORKER

Forerunner rate focused on the care and preservation of living things.

LOGIC PLAGUE

Viral code strings and insidious idea patterns which exploit the sensing-learning loop of Forerunner ancilla, causing them to either malfunction or transfer their allegiance to the Flood.

LUMINARY

Arcane Forerunner machines reengineered and employed by the Covenant to detect the former civilization’s relics.

MAC

Magnetic Accelerator Cannon, large electromagnetic mass driver used in human military applications like planetary defense and as capital ship weapons.

MAETHRILLIAN

Known by the Forerunners simply as “The Capital,” this massive world-station was the center of Forerunner life and politics.

METARCH

Hyper-advanced ancilla that administered significant portions of the ecumene’s regular operations.

MINER

Forerunner rate responsible for planetary and stellar engineering.

MINISTRIES

Overlapping bureaucracies tasked with executing decisions and interpreting guidance issued by Covenant leadership.

MISRIAH ARMORY

A leading manufacturer for human ordnance and matériel within the UNSC, its primary sites are located on Mars and formerly Reach.

MJOLNIR

A secret project that yielded the highly advanced armor used by Spartans.

MLA

Machine-Linked Autocannon, a powerful weapon employed by human vehicles.

MLRS

Multiple Launch Rocket System, a weapon used by human vehicles or stationary artillery.

MMG

Medium Machine Gun, a weapon utilized by human vehicles.

MONITOR

An ancilla tasked with administering control and maintenance of Forerunner installations or programs.

MOUT

Military Operations on Urban Terrain, combat operations within city environments.

MUTATION

Customized biological maturation used by the Forerunners to adopt or advance within a rate.

NANOLAMINATE

A type of material widely used by the Covenant for things such as combat harnesses and warship battle plating.

NEOTERIC

Referring to the redesigned Ark and Halo installations, ultimately activated by the Forerunners to eliminate all sentient life from the galaxy.

ODST

Orbital Drop Shock Troopers, a select group of marines within the UNSC Special Forces focusing on deployment behind enemy lines, usually via orbital insertion.

ONI

Office of Naval Intelligence, the primary strategic intelligence agency of the UEG, holding uncontested jurisdiction over espionage activities in the human sphere.

ORION

The UNSC’s first serious venture into creating super-soldiers in 2491 which would come to be officially known as the SPARTAN-I Project after 2513.

OTH SONIN

The home system of the Jiralhanae where Doisac and its three satellites (Warial, Soirapt, and Teash) were located.

OUTER COLONIES

The colonies with the furthest travel time from Earth, primarily viewed by inner colonists as resource sites on the periphery of UEG control.

PATH TOLGRETH

Forerunner name for the Milky Way galaxy.

PINCH FUSION

Covenant shipboard and station fusion reactors that use focused gravity generators to replicate conditions inside the core of stars.

PLASMA TORPEDO

Command link-guided projectile surrounded by a superheated plasma sheath.

POSTWAR

Referring to events taking place during the years following the Covenant War.

PRECURSORS

An ancient, technologically advanced civilization without apparent equal that governed the galaxy long before the Forerunners and humankind.

PRELATES

Biologically modified San’Shyuum super-soldiers with enhanced nervous systems and musculatures.

PRIMORDIAL

A being who represented the final progeny of Precursors and existed as an act of vengeance against the Forerunners for their genocidal crimes.

PROMETHEANS

An elite force of Forerunner Warrior-Servants led by the legendary Didact.

PROPHETS

See SAN’SHYUUM.

RECLAIMER

A Forerunner term referring to the chosen inheritors of the Mantle of Responsibility. After the firing of Halo, the surviving Forerunners passed this duty to humanity.

RECONCILIATION DEBT

Space-time damage instigated by causality violations and paradoxes resulting from using faster-than-light technology.

RED FLAG

A high-risk human naval operation planned in August 2552 in order to end the war, ultimately aborted during the Covenant’s attack on Reach.

REINTRODUCTION

The final stage of the Conservation Measure, restoring life to the galaxy after the activation of Halo by returning the catalogued and indexed species to their worlds of origin.

SACRED RINGS

The Covenant religious name for the Halo Array, which they believed would grant them divinity.

SANGHEILI

Also known as Elites, a strong, saurian species who once led the Covenant’s military.

SAN’SHYUUM

Also known as Prophets, the founders of the Covenant who occupied ministerial and clerical positions as the ruling caste.

SAP-HE

Semi-Armor-Piercing - High-Explosive, a type of human ballistic ammunition.

SENESCENT

Referring to the original Ark and Halo installations—known as Gyres—that were unable to effectively engage the Flood and were eventually replaced by the neoteric format.

SENTINEL

Forerunner machine tasked with a variety of roles, often encountered in large numbers collectively charged to maintain installations.

SFTE

Shaw-Fujikawa Translight Engine, human slipspace drive technology pioneered by Tobias Shaw and Wallace Fujikawa in the 23rd century.

SHIELD WORLD

Forerunner megastructure created to protect against the Flood and the effects of Halo.

SKEINS

The main cultural divisions of the Jiralhanae, the two most prominent being Rh’tol and Vheiloth.

SKIMMERS

Lithe and diminutive creatures currently allied with the Banished that share morphological traits with the Xalanyn.

SKIRMISHERS

See KIG-YAR.

SLIPSPACE

General term for a subset of alternate dimensions that can be utilized for faster-than-light travel and communication, shortened from the term “slipstream space.”

SPARTAN

A genetically enhanced and cybernetically armored human super-soldier of one of four military projects.

SPECIAL OPERATIONS

Classified military operations conducted by highly trained soldiers, also considered the military division that contains these specialized soldiers.

SSM

Surface-to-Surface Missile, rocket-propelled ammunition used by humans.

STAR ROAD

Untouchable and perpetual filament of neurophysical energy woven between dimensions by the Precursors.

STRIKECRAFT

Multi-phase interdiction vehicles utilized by a variety of factions, functionally equivalent to human fighter-bombers and interceptors.

SUB-MONITOR

Adjutants to the monitors of Forerunner installations, designed to provide support for the many operations of a given site.

TITHE WORLD

Key Covenant fortress and stronghold worlds that were able to serve effectively as proxies to High Charity.

TORSION PLATE

Forerunner subluminal drive that converts vacuum energy directly into thrust.

UEG

Unified Earth Government, humanity’s central governing body, based on Earth.

UNGGOY

Also known as Grunts, methane-breathing pseudo-arthropods that occupy menial roles within whatever faction they are conscripted.

UNSC

United Nations Space Command, military arm of the UEG, established in 2164. Following the Covenant War it has five branches of service: Air Force, Army, Marine Corps, Navy, and Spartan.

VISR

Visual Intelligence System, Reconnaissance, the most up-to-date HUD software used by UNSC personnel as of 2560.

VTOL

Vertical Take-off and Landing, referring to aerodyne vehicles which can launch and land vertically.

WAR OF ANNIHILATION

The Covenant’s name for their empire’s genocidal war against humanity.

WARRIOR-SERVANT

Forerunner rate responsible for the military defense of the ecumene.

WAVESPACE

Layers of slipspace with proximate terminations, through which near-instantaneous communication signals can be routed.

WEAPON-SHIP

Auxiliary combat spacecraft deployed in Forerunner naval warfare.

WRIT OF UNION

The peace accord between the San’Shyuum and Sangheili which formed the Covenant.

XALANYN

An enigmatic civilization that mysteriously survived the firing of the Halo Array and were subsequently imprisoned within Zeta Halo by a group of surviving Forerunners.

XEG

Xeno-materials Exploitation Group, a human organization within ONI that recovers, studies, and reverse-engineers alien technology.

YANME’E

Also known as Drones, a race of carnivorous insectoid arthropods who served the Covenant as mechanics and soldiers.