1) Alveolus 2) Cavity 3) Concave shape 4) Dent 5) Depression 6) Dimple 7) Dint 8) Excavation 9) Follicle 10) French word used in English 11) Hollow 12) Hollowness 13) Honeycomb 14) Incurvation 15) Incurvature 16) Indentation 17) Intaglio 18) Lacuna 19) Sinus 20) Solid 21) Strip mine 22) Trough 1) Basin 2) Concaveness 3) Dome 4) Fossa 5) Incurvation 6) Incurvature 7) Indentation 8) Indenture 9) Rut 
This image is of a CD single artwork that appears both on the CD and on a variety of different websites, and has been released on these sites to promote the single. It is being used on this page to illustrate 1 of the 4 different artworks used for The Automatic`s single Raoul (song). Cover from The Automatic`s single Raoul. Source: 7digital.com .....
• (n.) A concave surface, or the space bounded by it; the state of being concave.
A hollow or depression, with more or less evenly curved sides, on any surface. ... (05 Mar 2000) ... 
(kon-kav´ĭ-te) a depression or hollowed surface.
Con·cav'i·ty noun ; plural Concavities . [ Latin concavitas : confer French concavité . See Concave .] A concave surface, or the space bounded by it; the state of being concave. 
Type: Term Pronunciation: kon-kav′i-tē Definitions: 1. A hollow or depression, with more or less evenly curved sides, on any surface.
[n] - the property possessed by a concave shape
concavity 1. The state or quality of being concave. 2. A concave surface or thing; a cavity. 3. A hollow or depression, with more or less evenly curved sides, on any surface.
concaveness noun the property possessed by a concave shape
the state or quality of being concave. · a concave surface or thing; cavity.