1. A shape that curves or bends inward
   - concavity, incurvation, incurvature

Derived forms: concave shapes

Type of: solid

• genus Ouranopithecus
• genus Ovalipes
• genus Ovibos
• genus Ovis
• genus Oxalis
• genus Oxandra
• genus Oxybelis
• genus Oxydendrum
• genus Oxylebius
• genus Oxytropis
• genus Oxyura
• genus Oxyuranus
• genus Ozonium
• genus Ozothamnus
• genus Pachycephala
• genus Pachyrhizus
• genus Pachysandra
• genus Packera
• genus Padda
• genus Paeonia
• genus Pagellus
• genus Pagophila
• genus Pagophilus
• genus Pagrus
• genus Pagurus