Affixes

Many English words beginning in cata‑ entered the language from Greek with the prefix already attached: cataract (Greek kataraktēs, down-rushing); cataclysm (Greek kataklusmos, deluge—the word was originally applied to the Biblical flood); catarrh (Greek katarrhein, flow down); catapult (Greek katapeltēs, hurling down); and catastrophe (Greek katastrophē, a sudden overturning or down-turning).

Among modern formations are catabolism (Greek ballein, to throw), the process of breaking down food to release energy, and catalyst (Greek luein, loosen), a substance that speeds up a chemical reaction without itself being consumed.

The variant form cath‑ is used before h, as in catheter (Greek hienai, to let go); cathode (Greek hodos, way), the electrode through which electrons enter a device.

Cata‑ is not an active word-forming element; recent examples tend to be spelt kata‑ and some technical terms in cata‑ have alternative forms in k. Examples include katabatic, a local wind flowing down a hillside at night, and kataplexy (also spelt cataplexy), a state imitating death adopted by some animals when alarmed.