Concave, Hollow
The concave radical and the concave kanji are the same!
Know your radicals, yo!
おう
くぼ, へこ, ぼこ
None
If you call someone concave the 王 (おう) will find out and he'll have his guards turn you concave.
Watch your mouth around the 王. Have you ever seen a concave person? Yeah that's because they didn't live through it. 王s aren't very nice, you know.