Arbor affinitatis
A matrix of a person's in-laws and step-children. Cf. arbor consanguinatis.
Arbor consanguinatis
A medieval term for a matrix diagram to compute degrees of kinship. The starting or zero point is the ego cell, evidently named by an analogy with grammar, since it represents the singular first person at the start of the computation. The successive adjacent cells represent all that person's theoretically possible "blood relatives" in the past, present or future. By counting the number of cells crossed to a relation, the user is not only able to compute the degree or order of kinship or consanguinity (the number of generations, positive and negative), but also to visually understand the boundaries of this kinship system. Circumscribed kinship is still common today in many parts of Europe, such as the Duchy of Berg in Germany, where third or fourth cousins, for example, are considered in vernacular usage to be "non-relations". The diagram is also a mnemotechnic device with a geometrical flavour, a type of linealis descriptio (see below), to help the student grasp that such relationships follow regular patterns (Schadt p.32). The term "arbor" (tree) is misleading, since an arbor consanguinatis has no resemblance whatever to a botanical tree, and also has very little in common with the stemma. Instead, the figure must have its origins in geometrical methods, perhaps inspired by board games. Prompted by this misnomer (first demonstrably termed the arbor iuris in 800, then the arbor consanguinatis in the 12th century (Schadt pp. 15-16)), some medieval arbores consanguinates (???) were given tree-like decorations, but these excrescences in no way alter the true functions of these diagrams as tables and scales of all the viable combinations known to the laws of incest and of intestate inheritance. The related Visigothic legal texts use the Latin terms scala (a step) and gradus in reference to the same concepts (Schadt p 32).
Linealis descriptio
An ambiguous Latin term used by Cassiodorus. Anna Catharina Esmeijer offers the hypothesis that it is a term for an explanatory schematic diagram of the stemma type.
Heraldic term for an enclosing circle, and more loosely for emblems consisting of one or more concentric circles. In medieval and early modern manuscripts, it was conventional in stemma diagrams to draw a circle around each node. Some authors refer to this as a medallion or clipeus.
In English, a synomym for a genealogy, and by transference, for the written record of a genealogy. In this section of the Macro-Typography website I use the term in a narrower sense still to denote tree-like arrangements of text connected by lines or shapes. The Oxford English Dictionary gives the plural form of stemma as stemmata, and this remains current among text scholars when speaking of more than one stemma codicum (below), and among insectologists referring to stemma eyes of a larva. Stemmata is irregular Latin, since Latin-speakers treated stemma as a foreign word and employed a Greek plural form (the literal Greek meaning was "garland"). The pedantic Graeco-Latinate plural form stemmata in English, which involves a double "loan", creates a serious obstacle to bringing the term into wider use. The normal English plural form stemmas is therefore preferable.
Stemma codicum
A graphic representation in stemma form of how multiple manuscripts derive from an archetype. Errors and gaps are replicated by manuscript copying, allowing the scholar to guess what the original might have said and to construct a quasi-genealogical history of the codices, while "contamination" (evidence of alternative or dual parentage) may obscure the picture. The archetype, or root of the diagram, is almost always non-extant and can only be postulated as having existed. The method, known as stemmatics or stemmatology, has been widely used in medieval history, palaeography and philology. The Latinate plural is stemmata codicum: codicum is the genitive plural of codex (a bound book). See a David J. Birnbaum's proposal for XML encoding of such stemmata codicum.

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