An addition is any segment of text that a copyist introduces into the copied text (one that is not present in the exemplar). In the process of collating and editing the term addition is a relative one which only indicates that a segment of text which is lacking in the base-text is present in some witness(es), without making a judgement whether the addition is secondary or not.
Cf. its contrary omission, and types of errors.
References
– Havet, Louis. 1911. Manuel de critique verbale appliquée aux textes latins. Paris: Librarie Hachette.
In other languages
DE: Hinzufügung
FR: addition
IT: aggiunta / interpolazione
AC, CM