An orifice is a mouth, opening, or aperture. It describes a hole that is not necessarily large, but that allows passage or communication between two spaces or environments.
This biological and physical term is often used in scientific contexts (anatomy, fluid dynamics). It implies a more technical usage than terms like 'hole' and often refers to a specific, defined opening that serves a particular function, like allowing the flow of liquid, gas, or other materials.
VENT HOLE
PORTA
OPENING
APERTURE