Sometimes you use a tool for years and still have something new to learn. I'm talking about
vi(1), not vim or nvim, but nvi! (the OpenBSD ones at least.)
While I was reading NetBSD desktop pt.6 "vi(1) editor, tmux and unicode
I knew vim end emacs had abbreviations, but I never thought that vi has them too.
~/.nexrc is more rich:
ab #d #define ab #i #include