I'm using MS Word 2016 in Windows. Whenever I change the width of the window, the page size changes. That is, I click-and-drag on the right border of the window and make it, say, a little wider. When I do this, the page width (the point where text wraps to the next line) in MS Word gets bigger too: Both the "right indent" mark in the Ruler and the actual edge of the page get bigger along with the window resize. My margins are set to 1" all around and the page size is fixed (Letter), but that doesn't seem to affect this. I tried restarting MS Word and even rebooting, but nothing changed. This started suddenly a couple of weeks ago for no reason that I know of.
How can I get back to the page width being a function of the paper width (8.5" for Letter paper) minus the margins (1" left and 1" right), rather than my window width?