cat(a)- Also cath- and kata-.
Movement downwards; figuratively, wrong or inferior.
[Greek kata-, down.]
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.