Stemmatology is the global term denoting all scholarly and scientific studies involving a text's genealogy and stemma codicum. It is usually concerned with reconstructing such a stemma, but may also study stemmata in a more abstract sense (hence this lexicon's name). The term is usually used synonymously to stemmatics. As with many other fields the endings -ology (from λόγος 'word, meaningful or scientific utterance') and -ic(s) (the adjective forming suffix -ικὴ with an intended feminine τέχνη 'art, field of study') tend to be used for the same purpose, namely to label a 'scientific field about X'.
If a difference between the two terms is perceived, stemmatology tends to be the wider term, whereas stemmatics may be confined to the Lachmannian method.
The Latin term 'stemmatologia' was already in use in the early 18th century, e.g. in the title Stemmatologia Tigurina: Das ist Zürichisches Geschlechter Buch […] by Erhard Dürsteler. But here the stemmata it lists were people's genealogical trees and not yet those of manuscripts. The word stemmatographia was used synonymously (cf. J. Ramminger, stemmatographia, in ders., Neulateinische Wortliste. Ein Wörterbuch des Lateinischen von Petrarca bis 1700, URL: www.neulatein.de/words/1/001317.htm (used on 12.12.2014)).