Nerve-Cluster - a particular set of nerves controlling certain physical actions and also certain psionic energy flows.
Spectrum - a progressive flow of psionic abilities from either with an aspect; or a progressive flow of abilities that all steam from the same nerve cluster, but are from different aspects.
Affinity - ones ability or cluster of abilities that they are best at, usually a "natural" talent towards certain abilities
Abilities - These are the individual things that psionic energy can influence or perceive.
Aspects - These are the large groups that are related by what can be effected.
Areas - These are the smaller groups that are more closely related then Aspects.
Sub-Areas - These are the smaller groups that are more closely related then Areas.
Psionic abilties tend to flow in a spectrum. For example there are at least three distinct menatl based abilities. Where being able to read thoughts stops, and emotions begain is unclear. The abilties fade into each other. Likewise the nerve cluster have a flow to them as well. Each of the three magor nerve clusters have an area of abilities that they control.
Each person will personally have a certain aspect that they are more skilled as compared with the other aspects. Likewise the other aspect will fall into order as well. Most psion tend to have a spectrum of nerve clusters as well.
As an example I my self am best at the Psionic Energy Aspect. The nerve cluster I use best in that aspect is my skin and hands. I also happen to be best at the skin abilties in the mental and phsyical aspects as well. That is a spectural abilty line, mine happens to be easier then most to figure out.
Another might be best at the mental aspect, perhaps thought is thier best abiltity in that aspect. The thought ability is focused through the head. This means the person must be best at the other head foucused abilities in the other aspects, or they will use the other two nerve cluster for the other aspect; one for each aspect. For example if they were best at the Matter area in the phsycial aspect, then they should be best at the Direct Manipulation in the Psi-Energy aspect. If they were best at the Forces area, then they should be best at the Pattern area.
Head - This includes all of the head. The general areas in the head that are used as receptors and senders are the center front of the forehead, the temples, and crown of the head, and the opcepital lobe (bulb which connects the spine and skull).
Sternum - This is the solar plexus nerve cluster. It is located at the base of the sternum bone, where the ribs spilt apart.
Skin - All of the outer layer of skin.
Spine - Although not directly used for projection of psionic energy, being the second largest nerve cluster in the human body it produces a large amount of psionic energy.
Hands - While not an individual psionic body focus, the hands are often the most useful and controllable of the skin nerve cluster.
Head - This nerve cluster produces wave or laser formatted energy. Condensed energy that tends to pass through most materials. This tends to carry high amounts of energy but as little "impact". It also tends to travel further then either streams or fields. This format tends to have length but no volume.
Sternum - This nerve cluster tends to produce stream formatted energy. Slightly condensed, wider focused energy then waves or lasers. This tends to carry high amounts of energy that have "impact". Also this energy format is often effected by matter and will "bounce or bend". It tends to travel further then fields, but not nearly as far as waves or lasers. While this format mostly has length, however it has limited volume.
Skin - This nerve cluster tends to produce fields. Non-condensed, and tends to spread out in all directions. Although this format may have either low energy or high energy, in either case it has almost no "impact". It tends to create a barrier that generally only effects energy (however that energy may effect the energy with in matter as magnetic fields do). Matter will sometimes stop the "expansion" of the field but usually has almost no effect. It tends to take up the space given (the energy expanses until it reaches its diffusion point [the point at which the energy per square inch is no longer replied by its magnetic influences]). It does not travel as far as streams, lasers or waves do. However while it has no real length (as distance) it does cover volume.