What does nautilus mean?
A nautilus is a marine cephalopod mollusc with a distinctive spiral shell divided into separate chambers. It is a living relative of octopuses, squid, and cuttlefish, but it differs from them in retaining an external shell. The shell’s spiral is often described as logarithmic, making it a frequent subject in discussions of natural geometry. In everyday decorative contexts, “nautilus” may also refer to the shell itself, which is prized for its smooth form and intricate chambered structure. The word carries associations with the sea, natural history, and the mathematical beauty of spirals. It is especially useful when precision matters, since describing an animal simply as a “shelled fish” would obscure its place among the cephalopods and the unusual way its chambers function.
nounA marine mollusc with a spiral external shell divided internally into chambers, belonging to the cephalopod group that includes squid, octopuses, and cuttlefish. The shell is a distinctive symbol of the natural logarithmic spiral.
- A cephalopod mollusc with a spiral, chambered shell, especially the chambered nautilus.
- A nautilus shell used as an ornament or decorative object.
"The nautilus adjusts its buoyancy by changing the amount of gas in its shell chambers."
"The museum displays a large nautilus shell beside an explanation of the logarithmic spiral."
"She opened the glass case and found a polished nautilus on the desk."
The standard plural adds -es.
"Several nautiluses were visible in the aquarium."
A nautilus grows a spiral shell divided into chambers, and its close relatives include the squid, cuttlefish, and octopus.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of nautilus
The word comes from Greek nautilos, a term for a kind of sea creature and also associated with the spiral shell. Greek nautilos is related to naus, meaning “ship,” through the idea of a sailor or seafaring creature; English words such as nautical, navigator, and astronaut share this wider etymological family. The modern English meaning developed through natural-history and scientific usage for the chambered marine mollusc.
Related word forms
How nautilus is actually used
In biology, the term normally refers to the living mollusc; in decorative and collectible contexts, it can refer to its shell. The spelling is the same in British and American English.