What is a gloss in language?

In language, linguistics, and philology, a gloss is a brief explanation, definition, translation, or annotation of a word, phrase, or grammatical form, especially when the original term is obscure, archaic, dialectal, or in a foreign language. The practice of glossing is ancient. In medieval manuscripts, scribes wrote glosses between lines or in margins to help readers understand difficult Latin or Greek texts. There are different types. An interlinear gloss appears directly between lines, often giving a word-for-word translation. A marginal gloss appears in the margin. In modern linguistics, glossing is a technical tool used to show the structure of sentences in languages unfamiliar to the reader. For example, a linguist might write a sentence in Swahili and then below it provide a morpheme-by-morpheme gloss showing tense, person, and case markers, followed by a free translation. This is called Leipzig glossing. A glossary is a collection of such glosses, typically an alphabetical list of terms and their definitions at the end of a book. The purpose of a gloss in language is to make meaning transparent without replacing the original text, adding a layer of understanding.