What does cataract mean?
A cataract is primarily a medical condition in which the normally clear lens of the eye becomes cloudy, gradually blurring and dimming vision. It is strongly associated with ageing, though it can also be congenital or result from injury, and it is routinely treated with outpatient surgery that replaces the clouded lens. The word carries a second, older meaning: a large, powerful waterfall, used both geographically — as in the famous cataracts of the Nile — and figuratively, where a 'cataract of rain' or 'a cataract of applause' suggests something overwhelming and unstoppable. This dual sense reflects the word's origin: Greek kata- ('down') combined with raktēs ('rushing'), evoking water plunging downward. Today the ophthalmological sense dominates ordinary speech, while the waterfall sense survives mainly in literature, place names, and elevated prose. Knowing the word enriches both clinical conversation and descriptive writing about nature's grandest spectacles.
A clouding or opacity of the crystalline lens of the eye that progressively impairs vision.
"He put off seeing the optician until his cataracts made night driving impossible."
A large, steep waterfall; also, figuratively, a torrential rush or downpour of anything.
"A cataract of mud and debris swept down the hillside after the storm."
Regular plural; commonly used for the eye condition since it frequently affects both eyes, and for multiple waterfalls.
"Both of her parents had cataracts removed in their seventies."
The ancient Greeks thought a cataract looked like a waterfall pouring across your eye — the same word literally means 'down-rushing'.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cataract
The word derives from Latin cataracta and ultimately from Greek kataraktēs, formed from kata- ('down') plus arassein/rassein ('to strike, dash'), giving the sense 'down-rushing'. In classical usage it referred to floodgates, portcullises, and rushing waterfalls alike. English adopted the term in the late Middle Ages and early Renaissance, applying it first to great waterfalls and later, by the early seventeenth century, to the clouded condition of the eye's lens — an image likening the opacity to a waterfall obscuring the pupil. Its Greek prefix links it to cognates such as catastrophe and cataclysm.
How cataract is actually used
In everyday modern usage, 'cataract' overwhelmingly refers to the eye condition, so context is needed when using it to mean a waterfall. The waterfall sense is somewhat literary or geographical today. The plural is standard for the eye condition since people often have them in both eyes. The adjective 'cataractous' exists in medical writing but is rare outside it.
Easily confused with cataract
A catapult is a machine for hurling objects, whereas a cataract is either a clouding of the eye's lens or a large waterfall.