What is the meaning of "to annotate a passage"?
One annotates a passage that need explanation to be completely understood and appreciated. Often, in works of literature, an editor will annotate the text in the margin (or at the bottom of each page) to give the reader further insight into sources or information that could really bolster the reader's understanding.
Anyone can create annotations, so your inquiry about annotating "a passage," simply implies the task of either: making notes that analyze the specific wording found in the passage; providing source background information related to the passage; or referring the passage to another part of the same text.
Below, I've referred you to a couple of documents that could help you in planning annotation work for your students.
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