An opening, an orifice, or a short passage, especially in a bone.
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.