foramen

break crack crater cut dent gap mouth pit pocket tunnel void window

aperture breach burrow cave cavern cavity chamber chasm chink cistern cleft cranny den depression dimple dip excavation eyelet fissure fracture gash gorge hollow hovel keyhole lacuna lair leak nest niche nick notch orifice outlet passage peephole perforation pockmark puncture rent retreat scoop shaft shelter split tear vacuity vent

mountain

closing closure

opening orifice outlet stoma vesicle

sweat gland