noun
supplementary note; additional annotation
Used in academic or formal writing to refer to notes that supplement or clarify the main text.
論文の最後に補注を加えた。
I added supplementary notes at the end of the paper.
注釈 is a more general term for annotations or commentary, while 補注 specifically refers to supplementary notes added to a text.
Compound of 補 (supplement) and 注 (note).