What does acaleph mean?
An acaleph is a jellyfish — a free-swimming marine animal with a soft, gelatinous, often umbrella-shaped body and trailing tentacles armed with stinging cells. The term derives from the Greek 'akalēphē', meaning nettle, reflecting the creature's sting, and it was once used as the formal name for a class of such animals, the Acalephae, in older systems of zoological classification. Today 'acaleph' survives chiefly in historical and scientific writing, having been displaced in everyday English by the simpler word 'jellyfish'. It is almost always encountered as a noun, with the plural 'acalephs' (or the Latinized 'acalephae' in older texts). For readers of nineteenth-century natural history, where the word appears frequently, knowing that an acaleph is simply a jellyfish makes those vivid descriptions of drifting, luminous sea creatures immediately accessible.
nounA jellyfish; a free-swimming marine coelenterate of the former class Acalephae, having a gelatinous, typically umbrella-shaped body and stinging tentacles.
- A jellyfish; any member of the former zoological class Acalephae comprising free-swimming coelenterates with stinging tentacles.
"The tide had washed dozens of translucent acalephs onto the sand by morning."
"Naturalists of the nineteenth century grouped the acalephs together as a single class of stinging marine animals."
"Watching an acaleph pulse through the aquarium tank, she marveled at how much of its body was simply water."
The regular plural is 'acalephs'; older scientific texts may use the Latinized plural 'acalephae'.
"Hundreds of acalephs drifted past the research vessel's lights that night."
The word 'acaleph' comes from the Greek for 'nettle' — naturalists literally named the jellyfish after a stinging plant.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of acaleph
Acaleph comes from the Greek 'akalēphē', meaning nettle, adopted into scientific Latin as 'acalepha' and used by early nineteenth-century naturalists as the name of a class of stinging marine animals. The choice of name reflects the jellyfish's sting, likened to that of the nettle plant. As zoological classification was revised, the class Acalephae was abandoned, and the word is now largely historical.
Related word forms
How acaleph is actually used
Acaleph is a technical and now largely historical term, used mainly in older zoological literature; 'jellyfish' is the ordinary modern word. The plural is 'acalephs', though the Latinized plural 'acalephae' appears in older scientific texts.
Easily confused with acaleph
A cephalopod is a mollusc such as an octopus or squid, whereas an acaleph is a jellyfish — a cnidarian with a gelatinous bell.