Noun, Noun which may take the genitive case particle 'no'
emptiness; being empty
ほとんど空なのでガソリンを入れなくてはなりません。I need to put some gas in the car, as it's almost empty. Prefix
not carrying anything; unburdened; empty-handed
dishonoured (bill, promise, etc.); false; no-show (reservation); put-on (cheeriness, courage, etc.); empty (compliments); insincere
Also written 虚【から】