凹 /āo/ angolul

dimple [dimples]▼(small depression or indentation in generic surface)
noun
[UK: ˈdɪm.pl̩] [US: ˈdɪm.pl̩]

concave▼(curved inward)
adjective
[UK: ˈkɒŋk.eɪv] [US: kanˈkeɪv]