stemmatics
The study of multiple surviving versions of the same text with the aim of reconstructing a lost original.
uncountable
In other words, they must carry out an operation similar to the collations required by Lachmannian stemmatics, after which they must make a critical (i.e., subjective) choice. And, when constituting the text, they do not just slavishly copy their source, obvious errors included; their editions always contain an element of interpretation.
Where it comes from
From stemma, from Ancient Greek στέμματα (stémmata, “family trees, genealogy”).
Adapted from the Wiktionary entry stemmatics (CC BY-SA 4.0).