Game jargon. Some is in-character, some is out-of-character.
Arcane Connection – an item which is connected in some way with a target, such as hair or blood from a person, a piece of stone from a castle wall, etc. In the Hermetic system, having an arcane connection is the only way to cast a spell directly on a target that you cannot actually sense. Certain arcane connections also give a bonus to penetration against a target’s magic resistance.
Aura – an area suffused with supernatural power. Strength is rated 1-10, which corresponds to the aura’s modifier to all supernatural powers and activities.
Certamen – a formal system of dueling between Hermetic magi.
Covenant – a group of Hermetic magi living in a single community.
Domus Magnus – the central covenant of a House. How important it is varies between Houses.
the Gift – the inborn ability to manipulate magical energy, present in maybe 1 in 10,000 people. Usually carries the side effect of making everyone around you very uncomfortable.
Hermetic magic – a style of magic based on the almost scientific formulation developed by the wizard Bonisagus. It is generally considered to have the best balance of raw power and versatility, although other forms of magic may beat it in one or the other of these areas. The use of scientific methodology also makes Hermetic magic much more amenable than other styles to having new ideas integrated into the existing framework.
Parma Magica – the “magic shield” that contributes to the Order being as powerful as it is. Boosts magic resistance and blocks the negative social effects of the Gift.
Primus – the leader of a House. As with the Domus Magnus, how powerful or important this role actually is depends on the specific House.
Quaesitores – the legal arm of the Order. Most are members of House Guernicus, though not all.
Redcaps – the official messengers of the Order, identified by their eponymous hats. They are non-Gifted members of House Mercere, though they have the same legal privileges and protections as magi.
Regio – a supernatural region that exists as a separate demi-plane, connected to the mundane world but to some extent outside of it. Plural is regiones.
Sanctum – the area within a covenant that is the private quarters of one magus/maga, typically the laboratory, bedroom, and adjoining space. It is illegal to enter someone else’s sanctum without permission, and acceptable (or even encouraged) for magi to defend their territory with force if necessary.
Sigil – annoyingly, this word has two different meanings – a magical “signature” that is consistent across all spells cast by the same magus, or a physical token representing a magus’ right to vote at a tribunal meeting.
Summa – a book that broadly summarizes all knowledge of a subject. Can be studied multiple times, until your score in that Art or Ability equals the level of the book.
Tractatus – a book that goes into great depth on a narrow aspect of a broader subject. Can only be studied once.
Tribunal – a geographic region of the Order of Hermes. The same word is also used to refer to meetings of the magi within that region. The Grand Tribunal is a meeting of the entire Order, although only a limited number of representatives attend.
Vis – often referred to as “raw vis,” this is magical energy given physical form. Can be used to boost a casting roll, power a ritual or magic item, or studied for xp. It is very valuable to magic users (Hermetic or not), and is traded like currency within the Order.
Warping – side effects of exposure to the supernatural, whether over a long time or in a short, powerful burst.