Additum

Additum is a Latin term meaning "that which has been added," derived from the verb addere, to add. The form additum is the neuter singular past participle; Latin grammars also show related forms such as additus and addita for other genders. In practice, additum appears in Latin texts to indicate something appended or added to an existing thing.

In textual criticism and manuscript studies, additum is used to designate material appended to a text after its original composition. This can include marginal notes, insertions, amended readings, or supplementary passages introduced by later editors. In scholarly editions, such material is sometimes described as additum to distinguish it from the base text and the author’s original wording.

In legal and ecclesiastical contexts, additum may refer to an appended clause, codicil, or addition to a document. Latin legal formulae may describe portions of a decree or will that have been added later as additum or addita, with translations such as "the added part" or "the addition." The term thus functions as a descriptor for later insertions rather than for the primary text.

In modern reference works, additum appears mainly in discussions of manuscripts and editions rather than as a standard English noun. When rendered into English, it is typically translated as "added" or "the addition." The English-language vocabulary for analogous concepts more commonly uses addendum, addition, or appended material.

Overall, additum serves as a descriptive label in philology and law for items that were not part of the original text but were incorporated subsequently.