blank space; margin; blank canvas
Refers to empty space on a page, document, or surface; also used figuratively for potential or room to act.
I write notes in the margin of my notebook.
There is still room for flexibility in this plan.
Please leave some blank space at the bottom of the report.
I wrote the meaning of the word in the margin of the textbook.
I filled in the blank space on the poster with photos.
There's still blank space left on this page.