An opening; a hollow; a bending.
- A depression or cavity formed by a bending or curving.
- Anatomy A dilated channel or receptacle containing chiefly venous blood.
- Anatomy Any of various air-filled cavities in the bones of the skull, especially one communicating with the nostrils.
- Pathology A fistula leading from a pus-filled cavity.
- Botany A recess or indentation between lobes of a leaf or corolla.