A fonon (音素 onso / fonimu?, "phoneme" / "fonime") is the basic particle of all elements that composes the planet of Auldrant in Tales of the Abyss. Fonons are vibrations of energy that give sound and allow matter to be distinguished, essentially composing the entire universe, as well as its contents.
Since the beginning of Auldrant's history, fonons have existed within everything. They are split into six categories, each representing an particular element. Each of these fonons is associated with an aggregate sentience, a spirit that embodies the element as a sentient form. They are as follows:
Originally, only the first six types of fonons existed. After the implementation of the Planetary Storm theory, created by Professor Southern-Cross, a new type of fonon was discovered at the outer rim of the fon belt, the Seventh Fonon. This new type of fonon could be used to read the planet's memory and determine the future, eventually leading to a devastating conflict of global-scale proportions during the Dawn Age of Auldrant, known as the Fonic War. Wars over the Seventh Fonon raged across the lands, ending only when the miasma, a poison from within the planet, covered the surface of the planet. Soon after, Yulia Jue, a woman skilled in prophecy, appeared.
Yulia foresaw 2,000 years into the future, later recorded and thereafter known as the Score, and discovered a way to seal away the miasma. Through the guidance of her prophecies, humanity sealed the miasma deep within the planet using the power of the Sephiroth Trees, and thus, creating the Outer Lands. Fonons are the basis of science and technology on Auldrant. Over time, humankind has learned to utilize them and execute fonic artes. Also, with the aid of machinery, humans have developed fon-technology that assist in many technological processes, such as the infamous fomicry. Unlike any fonon, the Seventh Fonon is solely used by dedicated fonists as a means of healing and replicating objects or living creatures. The other elemental fonons are used for dealing damage of a specific elemental type.
Despite the many applications the Seventh Fonon has, it can also lead to misfortune. If one who does not possess the affinity to control the Seventh Fonon tries to execute a fonic arte that requires its use, the arte can easily go out of control. An example of this occurs occurs in the story when a young Jade Curtiss attempts to use the Seventh Fonon to impress his teacher, Gelda Nebilim, but fails to control the fonic arte, setting the residence on fire and killing the professor. Over-absorption of the Seventh Fonon can be fatal as well. If one were to be implanted with a large quantity, every fonon in their body would mutate. Soon after, the body would begin to reject the fonons, leading to neural contamination and a type of induced madness, evident in Mohs's case.