To make clear with a note between brackets

grammar

To add an explanation in parenthesis or in the margin of a text is "to gloss" the text. The comment itself is a gloss.

gloss (2) source Oxford Dictionaries

noun
1. A translation or explanation of a word or phrase.

1.1 An explanation, interpretation, or paraphrase of a text.

verb [with object]
1. Provide an explanation, interpretation, or paraphrase for (a text, word, etc.)

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