The Lewis theory of acids and bases extends well beyond the things you normally think of as acids and bases and states that…
A Lewis acid is an electron pair acceptor
A Lewis base is an electron pair donor
The reaction above contains both a Lewis diagram of ammonia and boron trifluoride, and also is an example of a non-aqueous Lewis acid and base reaction not addressed by the other theories
https://en.wikipedia.org/wiki/Gilbert_N._Lewis