how do I reinstall windows defender for windows 10

Assuming the upgrade was offered & installed via Windows Update => Does the behavior persist if you run the Norton Removal Tool (and reboot) and then the McAfee Consumer Products Removal Tool(followed by another reboot) anyway?

[You cannot "reinstall" Windows Defender.]

It does not install. Error code 577

My message was that Windows Defender was closed.  I was hoping that it would have been more information as to how to reinstall.  Did not mention error code 577

Please answer all four (4) questions by number:

1. Did the computer come with Win10 preinstalled or did you upgrade a Win7 computer or a Win8.1 computer [<=PICK ONE!] to Win10?
2. Has a Norton application or a McAfee application EVER been installed on the computer since you bought it?
3. Did a Norton free-trial or a McAfee free-trial [<=PICK ONE!] come preinstalled on the computer when you bought it? (Doesn't matter if you never used or Activated it.)
4. Have you ever run the Norton Removal Tool and/or the McAfee Consumer Products Removal Tool?

1.  Upgraded from Windows 7
2.   No
3.    No
4.    No  I am using AVG Optima

It does not install. Error code 577

Please answer all four (4) questions by number:

1. Did the computer come with Win10 preinstalled or did you upgrade a Win7 computer or a Win8.1 computer [<=PICK ONE!] to Win10?
2. Has a Norton application or a McAfee application EVER been installed on the computer since you bought it?
3. Did a Norton free-trial or a McAfee free-trial [<=PICK ONE!] come preinstalled on the computer when you bought it? (Doesn't matter if you never used or Activated it.)
4. Have you ever run the Norton Removal Tool and/or the McAfee Consumer Products Removal Tool?