Forerunner symbols

The Forerunners used several forms of symbols and glyphs to convey a variety of meanings. These symbols can be found on Forerunner technology and within Forerunner installations, including the Halo Array. The Covenant later adopted these symbols for their writing system as well as religious imagery and as such, they are also commonly seen in Covenant technology and architecture.

Background
While the specifics of Forerunner languages such as Jagon and Digon remain a mystery, with only a handful of words known, the writing system they used to convey meaning is far better understood. The Forerunners appear to have used two different writing methods; the first was a system of glyphs or logograms, rather than parts of an alphabet, highly contextual in nature, with the meaning of different glyphs altered by order and context, and further meaning could be derived if the reader used more three-dimensional interpretations; when combined with different glyphs, a symbol might have radically different meanings, making individual glyphs pictograms or ideograms.

The second mode seems to be a more conventional writing system, using two-dimensional characters. There appear to be at least two variations of this conventional script. One type, observed in Forerunner relics on Installation 00, either inscribed onto stone relics or in holographic form,  involves highly complex characters resembling digital patterns or bar codes written vertically. In the other writing system, the characters are considerably simpler, consisting of a series of dots, squares, bars and triangles. The Covenant script is derived from the latter, although they use highly embellished variations of the original characters used by the Forerunners.

Other symbols found on Forerunner relics and structures are even less obvious in their meanings. They are obviously decorative in nature, but they are often larger and more elaborate in nature than their glyphs, and may depict specific shapes and forms, and may have more in common with petroglyphs than logograms.

The glyph system was also adopted by the Covenant as religious symbols, despite having little idea as to the true meanings of the original symbols; the most notorious example is their mistranslation of the "Reclaimer" glyph as meaning "Reclamation". Forerunner glyphs are found on Covenant Luminaries as indicators of Forerunner relics, as the Reclaimer glyph was seen to represent humans on Harvest. Humans in general have had little success in translating Forerunner texts, with the notable exception of Dr. Catherine Halsey.

Numbers
Only the Forerunner symbols for numbers one through five are known, though a base symbol with unknown meaning has also been found. It is probable that they also have a symbol for 0, but they may use a base 6 system and not have any more numbers. The base symbol may be the number 0.

The visual features of numerical glyphs differ slightly from those of normal Forerunner glyphs. Like the other glyphs, numerical glyphs use a circle as a base. However, the only features seen on numerical glyphs are concentric circles and arcs, radial lines, and the occasional radial line with a small circle on its end.

Eld
The glyph representing the Mantle of Responsibility, the main belief system of the Forerunners, is perhaps the most ancient and ubiquitous Forerunner glyph. Known as the Eld or the Tree-mark due to its resemblance to a heavily stylized tree, the symbol appears frequently on Forerunner structures and installations due to the Mantle's all-encompassing nature in Forerunner society.

Among many other sites, this symbol appears inside and outside Installation 04's Silent Cartographer, as well as on Installation 05 in various areas. It also appears on the Ark's surface, if viewed from space. It also makes an appearance in the Terminals throughout the Ark. The symbol also appears on top of a Monitor's "head" and behind the "eye" on the center orb. The surface of Requiem also bears the symbol, and the symbol is found in a wall on Requiem, accompanied by the inscription "Guardianship for all living things lies with those whose evolution is most complete. The Mantle of Responsibility shelters all.". A similar symbol was found on Installation 03 and moved to Ivanoff Station to be studied.

Shield World
Shield Worlds are represented by a symbol described as a "double-lobed icon". The symbol was described when Dr. Halsey was compiling her data with the AI Endless Summer. While Dr. Halsey was working, CPO Mendez asked her what the symbols on the screen are. Dr. Halsey replied that they are Forerunner symbols from the ruins on Onyx, and their theoretical translations. As she continued to work, Mendez then asked the meaning of a double-lobed glyph. Dr. Halsey replied that the symbol, roughly translated, means Shield World.

Reclaimer
The Forerunner glyph representing a Reclaimer is identical to the Marathon symbol, although the same symbol appears to have been in common use in Forerunner constructs, including the "eye" of 343 Guilty Spark, as well as the frontal section of an Enforcer. However, after Halo: Reach, later media featured a more vague appearance of the original symbol.

The original Marathon symbol is also used by humans in various instances, and it is the ship emblem of the. It is unknown if this is simply a coincidence, or if there is a relation to their status as Reclaimers.

Sigils
A sigil is a symbol representing a specific Forerunner, ancilla, or any other entity. They were often used to label transmissions, or to indicate affiliation with a given individual; for example, members of Master Builder Faber's personal security carried his sigil.

Installation symbols
In Halo 3, a number of details about the Halo Array arise. In the Ark's Citadel, where the Prophet of Truth attempted to fire the seven Installations, each Installation is shown in detail. Each Halo has its own hologram showing its structure and status, as well as a holographic symbol identifying each Installation. Some notes say that there are two versions of each symbol, one where the player enters the ring room and the view from the pedestal.

Symbol analysis
The symbols are primarily composed of circles and curves. Each glyph appears to use a circle as a base shape, often combined with either a concentric circle or fragments of one. Another common trait is the presence of one or more circular arcs whose osculating circles' centers lie on the base circle. Non-circular arcs and small non-concentric circles can be seen on some glyphs. The filling in of areas is uncommon but has been seen in Forerunner glyphs.

According to Bungie employee Joseph Staten, the blue and red signs denote the safety of the area -- that is, whether or not the Flood are present. Taking a closer look at the symbols, their locations, and what has been said by Bungie, the following can be deduced:

All of the others are found in various Forerunner structures, mostly on the levels 343 Guilty Spark, The Silent Cartographer, and The Library.

Cropped symbols analysis
Several of the symbols are variations of each other. There are a total of 16 unique symbols; the other 8 are rotations or croppings of the 16 main symbols. Of note is the fact that the cropped versions may not have been intended to be cropped; their in-game textures may have been inadvertently placed such that they extended beyond the edges of the polygons they were on, causing the parts that couldn't fit to be clipped. For sake of being thorough, however, they have been included as separate symbols.

Trivia
The base numerical glyph was used as an avatar by AdjutantReflex.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Halo Graphic Novel
 * Second Sunrise over New Mombasa
 * Halo: Ghosts of Onyx
 * Iris
 * Halo 3
 * Terminals
 * Halo: Contact Harvest
 * Halo: Reach
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo 4
 * Terminals
 * Spartan Ops
 * Halo: Escalation
 * Halo 2: Anniversary