To add notes or comments to a text, book, or document, explaining or critiquing its content. The professor asked the students to annotate the article with their thoughts and questions.
To mark or highlight a text with symbols or notes for the purpose of analysis or study. She likes to annotate her textbooks with different colored pens to organize her study notes.
To add explanatory metadata or labels to data (such as images or audio), especially for use in computing or machine learning. The team annotated thousands of images to train the recognition model.