Radical: check 4 paintings ***5 paintings.

Concave means two things.

1 concave āo-shape is high around and low in the middle [concave; Hollow; Sink; Concave] Its lake is not concave and convex, and Pinghu is uncontroversial. -"The Miraculous Classic, the Northern Famine Classic" is another example: concave shore; Concave surface; Depression (depression); Concave ground; Concave detailed explanation

Taiwan Province people often say "concave", that is, Minnan dialect (Minnan dialect), that is, the so-called Taiwanese dialect, which means "perseverance, perseverance, and the intention to get through", meaning concave: being forced by others, being forced by powerful people, and hard concave: picking holes, refusing to recognize accounts, and trying to be brave.