Gloss and glossary

https://en.wikipedia.org/wiki/Gloss_(annotation)

“A gloss is a marginal notation regarding the main text in a document. Shown is a parchment page from the Royal Library of Copenhagen.

A gloss (from Latin glossa; from Greek γλῶσσα glōssa, meaning ‘language’) is a brief notation, especially a marginal one or an interlinear one, of the meaning of a word or wording in a text. It may be in the language of the text, or in the reader’s language if that is different.

A collection of glosses is a glossary. A collection of medieval legal glosses, made by glossators, is called an apparatus. The compilation of glosses into glossaries was the beginning of lexicography, and the glossaries so compiled were in fact the first dictionaries. In modern times a glossary, as opposed to a dictionary, is typically found in a text as an appendix of specialized terms that the typical reader may find unfamiliar. Also, satirical explanations of words and events are called glosses. The German Romantic movement used the expression of gloss for poems commenting on a given other piece of poetry, often in the Spanish Décima style.”