verb
annotate
AN-uh-tayt/ˈænəteɪt/
To add explanatory notes or comments to something.
The woman annotates the leaf illustration with a label pointing to a vein.

Etymology
The pieces connect annotation with marking or noting something down. A note could be a mark drawing attention to a passage, then a subsidiary statement explaining it—the function of an annotation.
In context
social reading if you're not familiar with it is an internet-based activity in which students collaboratively read annotate and comment upon a shared text
More examples
- She annotated the map to show the blocked roads.
- We annotate each photograph with its date and location.
- He is annotating the manuscript for a new edition.
Forms
annotate · annotates · annotated · annotating
annotation noun — An explanatory note added to something.