Marginalia
/ˌmɑːrdʒɪˈneɪliə/
Definition 1 of 1
Pro Tip 1/3Academic Use
Marginalia are often used in academic settings to note important ideas or questions while reading. 
She added marginalia to the article to prepare for her thesis discussion.
Pro Tip 2/3Reflect Personal Thoughts
Marginalia can reflect personal responses or emotional reactions to the text being read. 
His marginalia were passionate, showing his strong disagreement with the author.
Pro Tip 3/3Historical Insights
Marginalia in old books can provide historical insights into how past readers engaged with the text. 
The historian was excited to find marginalia from the book's original owner in 1823.