How can I backup my abbrev_defs file every time it is changed, just like
any other file in emacs, please? And, logically, to the same place, my
'~/.emacs.d/backups' directory?

Thanks
Sharon.
-- 
A taste of linux = http://www.sharons.org.uk
DrugFacts = https://www.drugfacts.org.uk
Debian 10.1, fluxbox 1.3.7, emacs 26.3, org 9.3