Expressions (phrases, clauses, etc.), Adverb (fukushi)
still more; to say nothing of; not to mention
Usually written using kana alone
それらの星は肉眼で見える、まして望遠鏡ならなおさらである。You can see the stars with your naked eye, and even better through a telescope. still less
Usually written using kana alonewith neg. verb
Also written 増して【まして】