A small opening or orifice, as in a body organ or passage.
Any of the small openings or pores in a sponge.
The mouth of a river.
A small opening in a membrane; a surgically constructed opening, especially one in the abdominal wall that permits the passage of waste after a colostomy or ileostomy.
One of the tiny pores in the epidermis of a leaf or stem through which gases and water vapor pass.
A mouthlike opening, such as the oral cavity of a nematode.
An artificial anus.