Below is a list of cave vocabulary.  Definitions of formations are a subcategory under Speleothem.

Aquifer – Rock or soil layers beneath the water table that store and transmit useable amounts of water.

Calcite – Calcium carbonate (CaCO3) crystallizing in the hexagonal system.  It is the mineral of which limestone and speleothems are composed.

Carbonic acid – Produced when carbon dioxide combines with water.  It dissolves limestone to form caves.

Cave – Naturally formed, hollow chamber in the earth or in the side of a hill or cliff.

Cavern – Interconnecting series of caves.  Sometimes defined as caves with speleothems.  Sometimes the words cave and cavern are not differentiated.

Echolocation – Use of reflected sound by bats (and some other animals) to locate objects.

Groundwater – Water that exists underground in saturated zones beneath the land surface. The upper surface of the saturated zone is called the water table. It fills the pores and fractures in underground materials such as sand, gravel, and other rock, much the same way that water fills a sponge. If groundwater flows naturally out of rock materials or if it can be removed by pumping (in useful amounts), the rock materials are called aquifers.

Hibernation – State of greatly reduced activity and metabolism, occurring in winter.

Karst – Irregular landscape formed by dissolution of soluble rocks (predominantly limestone) marked by sinkholes, streamless valleys, springs, caverns, and underground drainage systems.

Limestone – A sedimentary rock composed mainly of calcium carbonate.

Sedimentary Rock – Rocks formed by the accumulation of sediments.

Show Cave – A cave open to the public with improvements such as lights, stairs, railings, and pathways.

Sinkhole – A surface depression in the ground caused by collapse due to the solution of underlying rocks.

Solutional Cave – Formed when soluble rocks are dissolved by slightly acidic water.

Speleology – The study of caves.

Speleothem – Commonly known as cave formations, formed by the deposition of minerals from water.  These include:

Soda Straw – Thin-walled, hollow tubes growing from cave ceilings as water runs through the tube and leaves a ring of calcite at the tip.

Stalactite – Forms as calcite is deposited as water runs down the outside of a soda straw when the hollow tube becomes plugged with minerals.

Stalagmite – Grow up from the floor when mineral rich water drips from above.

Columns or Pillars – Any cave formation that touches from floor to ceiling, most commonly when a stalactite and stalagmite grow together.

Helictites – Small, twisted structures projecting from ceilings, walls, floors, and other speleothems that seem to defy gravity.  Formed by capillary action, they project at all angles.

Flowstone – Resembles frozen waterfalls and forms when water flows down sloped surfaces, depositing calcite in sheets.

Drapery – Forms when water runs down an inclined ceiling or wall, it deposits calcite in thin, translucent sheets.

Bacon – Thin draperies formed when the water contains minerals (usually iron oxide) in addition to calcite, resulting in dark orange or brown bands.  When a light is shown behind it, it resembles bacon.

Cave popcorn (formerly cave coral) Small, knobby clusters believed to form either by seeping water or condensation.

Rimstone Dams – Step-like terraces on floors that enclose pools of water behind them.  They form as water loses its carbon dioxide as it flows over the edge of the dam.

Boxwork – Composed of fins of calcite that may crisscross at various angles to form hollow chambers within.  Their shape resembles cardboard dividers in packing boxes.  They form when calcite is deposited by water in cracks in the rock.  The original rock erodes, leaving the more resistant calcite.

Troglobite – Animals that spend their entire lives in the darkness of caves.  They show high levels of adaptation to total darkness.  Many are sightless and without pigment.  Examples include blind cave fish, millipedes, flatworms, isopods, and insects.

Troglophile – Animals that spend most of their life in caves, but with the ability to survive outside.  Cave beetles, cave crickets, and salamanders are examples.

Trogloxene – Animals that live above ground, but go into caves for shelter.  Skunks, raccoons, bats (sleep in the cave and hunt outside) and humans are examples of trogloxenes.

Water Table – The surface below which all empty spaces within the rock are filled with water.