connective N1 rare literaryarchaic
況や — let alone / much less / to say nothing of ~
況や ・ いわんや
A full written guide for 況や is on the way.
This point is mapped in the grammar tree, but its examples, formation table and usage notes haven't been written yet. The fastest way to learn it now is to meet it in real sentences inside Jengo.
See 況や in real sentences
Jengo shows 況や the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Advanced Japanese Grammar. Editorial confidence: medium.