The 7th Fonim
The Fonim in which Dr. Southern Cross discovered in BD 2695. Its Fonim Frequency is 3.141592653589~ (just imagine 22/7 or Pi). One of its merits is to have the ability to heal. Also, if this Fonim is used, it is possible to read the "Memories of the Planet". Memories of the Planet means the past and the future of the Planet. The Fonic War was ignited along with this discovery, but it was stopped later when Yulia tells people of the miasma and the future. The collective conscious of this Fonim is called "Lorelei". Theoretically it has been proven that it exists, but it is has yet to be confirmed.
Big Bang
A symptom that happens to the Original of the Replica [Complete Isotope]. A phenomenon that happens in order for the Original to reform itself by retrieving the information of the Replica [that shares the same existence], and absorbing the Replica that is undergoing Dissonance.

[Note: Replica is just a general term. Therefore, it comprises of two different classes - Isotope and Complete Isotope.]
Cell Particles
The energy which floats in the core of the plant of Auldrant, it is also called the Memories of the Planet. In BD 2677, Dr. Southern Cross proposed the idea of using the Cell Particles through artificial means in order to create an eternal energy source for mankind, that is also when Planet Storm was formed. The root of power of Artes and works related to Fonims were brought along by the Planet Storm.
Closed Score
This Score won't be available to most people unless they are higher than the ranks of being a Maestro in the Order of Lorelei or the fact that they're from the royalty bloodline. This Score contains highly classified information on what important figure will die and places on Auldrant that will be destroyed...etc. For normal/low ranked soldiers in the Order of Lorelei, it is a death sentence if they wish to investigate on the Closed Score. It seems that the laypeople only knows no more than its existence.
Complete Isotope
Means an existence that shares the same Fonim Frequency as the other. For example, Luke and Asch, Star and his Replica. Dist completed the theory from the part where Jade left off and he successfully replicated Star just like 7 years ago [when Luke was made]. However, all the Fonmachines used to engage in the experiment were broken after [during] the experiment; therefore, all the information pertaining to how it was done were gone.
A phenomenon that happens when the matters with the same frequency as the other object is being dissolved as Fonims, through which the Fonims are being taken in. It shouldn't happen unless the person him/herself or others uses a special type of Arte, but it seems it is much more easier to see this phenomenon happened to Replicas. In Luke's case, he didn't intend to make this happen because he's a Replica and he also took The Orb of Lorelei [which is filled with the 7th Fonim].
A side effect of Fomicry when the Original started to feel that his/her strength and his/her Fonims are escaping. It is closely similar to feeling weak and on the verge of fainting. In most cases, this may result in death on the Original. However, if the Original can live through this or without experiencing this side effect, when this period ends and if the situation is optimal, the Big Bang will occur.
The vibration layer which creates the planet. It is formed by many different Fonim alignments and it is arranged from the outside to the inside by Light, Fire, Water, Wind, Earth, Darkness. It was later discovered by a portion of Fonist (mainly Dr. Southern Cross) who realized there is a 7th Fonim floating in the Fonbelt as well.
From the 1st to the 6th, they are all assigned an alignment. Since the 7th Fonim is made with the combination of Fonim and Cell Particles, it is neutral. When the Fomins are gathered and collected to a certain amount, it will become an entity of Fomin that has a "will". It is confirmed that there is such an entity from each of the Fonims from the 1st to the 6th Fonim. Because everything is composed of Fonims and elements, it seems that when the Fonims inside a person's body is gone (or elements are in disorder), the flesh will also disappear. A good example of that will be the scene at the tower of Rem, where the Replicas are destroyed because the Fonims inside them are were taken away.

Speaking of which, if you talk to a soldier back in Grand Chokmah, he'll tell you that if you use too much Fonic Artes, the amount of Fonims contained in your blood will be lower than usual. (I guess in a certain sense, if you use too much Fonic Artes, you will die 8D?)
Fonim and its Alignment
The 1st Fonim: Darkness (Shadow)
The 2nd Fonim: Earth (Gnome)
The 3rd Fonim: Wind (Sylph)
The 4th Fonim: Water (Undine)
The 5th Fonim: Fire (Ifrit)
The 6th Fonim: Light (Rem)
The 7th Fonim: Fon (Lorelei)
Fonim Frequency
This has the same meaning as Characteristic Frequency. In other words, it works like finger prints where there is no other person that shares the same as yours.
A substance that is needed in order to complete Fomicry. It can be obtained from the ancient minerals in the Ortion Cave.
A Fonstone will be created when the Memories of the Planet is being read and chanted. Because of the amounts of materia chanting by Yulia was massive, the Fonstones became the size we see in the game right now. In order to know the future of the planet, there were many disputes caused by this in the past. The war between Kimalsaca and Malkuth was also started for this reason (Read: ND 1401, The first War of Borders on the Timeline).
The Grand Hymn
The song in which Yulia made a pact with Lorelei. Comprised of the 7 songs remained by Yulia, and it will be completed when they are chanted one after another. This probably serves the function of unknown symbolism, since it is the evidence which Yulia used as the pact with Lorelei. It seems that Yulia used the Key of Lorelei and the Grand Hymn to summon Lorelei in the past.
When the Fonims between people with the same Fonim Frequency interferes with one another. This is also called the "Southern Cross Effect", where a complete anti-fonic energy is created.

For example, in the very beginning of the game, the Hyperresonance created by Luke and Tear is all due to the same frequency of the 7th Fonim floating inside their body.
Key of Lorelei
A Fonweapon that is created by Yulia in order to borrow the powers of Lorelei. The weapon is composed of pure 7th Fonim and is made with two parts, "The Sword of Lorelei" and "The Orb of Lorelei". It was said that Yulia had Lorelei reside in the sword and utilized Lorelei's power freely. This is also how Yulia caused the reoccurance of Planet Storm in the past. The Sword of Lorelei is said to have the power to gather the 7th Fonim while the Orb of Lorelei has the power to proliferate the 7th Fonim. By the way, it seems the Orb can take the form of a Fonic Fork.
The collective conscious of the 7th Fonim. It is also the only existence which knows the future of the planet.
The Order of Lorelei
A religious sect created by Yulia (in fact, it's Francis Daath), which she proposes by knowing the future, it can save people from destruction. It was established also because it guides people and to protect the Scores in order maintain the prosperity of Auldrant. The dominion of Daath serves as a split copy with the same function of Yulia City (to monitor) on the outer shell. It is also made explict that only the Fonemaster can chant the Planet Score. It can also be said that the world takes the lead from the shadow, because the one in power cannot tell people the Scores at a moment's notice and use his/her right to give Closed Scores (to the royalities) to show his/her favors.
The opposite meaning of Replica, which means the one that is being experimented through Fomicry. To living organisms, there will be disorders, and in extreme cases, they will die. However, as long as they have passed the abnormalties causing period, there wouldn't be a problem unless their bodies are trying to absorb the information from their Replicas (Read: Big Bang). In Asch and Luke's case, because Luke has been created for 7 years and nothing has happened in between, this is probably not exactly suitable to refer Asch (Read: The Key of Lorelei --> Dissonance).
Planet Storm
It's a reaction where the Cell Particles from the core was blown out of the Radiate Gate towards the Fonbelt, then float through the Fonbelt, then enters into the Absorption Gate and returns back to the core. When the Cell Particles flow through the Fonbelt, they will combine with all the other elements to form the 7th Fonim.
What used to be the crust of Auldrant. It is covered by a sky filled with miasma and the outer crust, and it is currently floating on the mantle which is a part of a liquified crust.
An Isotope that was created by Fomicry. It originated from Jade's theory when he was around 11-12. It involves using the 1st to the 6th Fonim, but because he couldn't stablize these Fonims at the time, it caused the Replica!Nebilim to have a feriocious hostility and disordered mentality. Because of that, the Replicas that are created later down the road is filled with the 7th Fonim. For that reason, that is why instead of using a huge number of 7th Fonist at the Tower of Rem, the Replicas were used in replacement.

[NOTE: Again, as mentioned, Isotope DOES NOT equal to Complete Isotope.]
The Memories of the Planet. People's life [stories], the way in which the planet is heading towards is also chanted through the Scores. In order to chant this, one must have the ability to use the 7th Fonim. The Scores that Yulia chanted around 2000 years ago became the Fonstones that are now floating in the sky. Those Fonstones were engraved with the way the planet is heading towards, and that is why it is also called the "Planet Score". In Tales of the Abyss, there are two types of Scores, one of them being the ones that you read directly off the Fonstones, the other being the ones that you read anew by using the 7th Fonim.
Selenia Flower
A nocturnal flower. It is the only flower that is cultivatable in the Qliphorth. It is also abundant in the Tataroo Valley.
The fon slots of the planet, where the Fonims of the planet are gathered, as well as a place where the Cell Particles exit. The Sephiroth Tree serves as an powerful artificial means to allow the Cell Particles to leave these Fonslots. It is also considered as a support for the outer crust to lean against to escape from the miasma filled Qliphoth. To fully control all the Sephiroth, one must break the 3 different phases of seals casted onto each Sephiroth.

The first phase: The Daath Seal, which guards the entrance to the Passage Rings.
The second phase: The Albert Seal, which was casted onto the 5th and the 8th Sephirot in order to stop the controls between Sephirots. (As in, a stop to prevent what Luke and company did by reactivating the 5th and the 8th to gain controls to other Sephirots that are inaccessable during their time.)
The third phase: The Yulia Seal, which Yulia herself placed on the Passage Rings.

The 1st Sephirot: Radiate Gate
The 2nd Sephirot: Absorption Gate
The 3rd Sephirot: Shurrey Hill
The 4th Sephirot: Zao Ruins
The 5th Sephirot: Akzeriuth
The 6th Sephirot: Tartaroo Valley
The 7th Sephirot: ?
The 8th Sephirot: Hod
The 9th Sephirot: ?
The 10th Sephirot: ?
The Technology of Fomicry
A technology that exists in order to replicate. Though it is possible to perform such operation onto inorganic and organic matters, it is generally unable to replicate the same Fonim Frequency as the Original. Hence, the Replicas usually come out as something that looks the same on the outside, but is different on the inside.
Yulia's Hymns
This means the 7 songs that Yulia remained. Usually, [just by chanting] the songs alone cannot bring out the Artes, but Yulia's songs are different and they hold the same power as Artes. Yet, it is impossible to have any reaction if one only knows the tune without knowing the true meaning (symbolism/metaphors/allusions) to the songs.