platypus

American  

[plat-i-puhs, -poos] / ˈplæt ɪ pəs, -ˌpʊs /

noun

platypuses, plural platypi plural

1. a small, aquatic, egg-laying monotreme, Ornithorhynchus anatinus, of Australia and Tasmania, having webbed feet, a tail like that of a beaver, a sensitive bill resembling that of a duck, and, in adult males, venom-injecting spurs on the ankles of the hind limbs, used primarily for fighting with other males during the breeding season.

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platypus British  

/ ˈplætɪpəs /

noun

1. See duck-billed platypus

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Usage

Plural word for platypus The plural form of platypus can be either platypuses or platypi, pronounced [ plat-i-pahy ], but platypuses is more widely used. The plurals of several other singular words ending in -us are formed in the same way as platypuses, such as virus/viruses, sinus/sinuses, and walrus/walruses. Irregular plurals that are formed like platypi, such as cactus/cacti and fungus/fungi, derive directly from their original pluralization in Latin. However, the standard English plural -es ending is often also acceptable for these terms, as in cactuses.

Etymology

Origin of platypus

1790–1800; < New Latin < Greek platýpous flat-footed, equivalent to platy- platy- + -pous, adj. derivative of poús foot

Explanation

What animal has a duck bill, fuzzy kitten belly, beaver tail, and poisonous webbed feet? A platypus! A platypus is a wacky mammal that mainly lives in the water off Australia. Although a platypus is a mammal, it lays eggs. Because of its distinctive bill, the platypus is often called the duck billed platypus. It's an unusual animal, defying many of the usual characteristics of a mammal — the platypus lays eggs, is aquatic, has a tail like a beaver's, is venomous like a snake, and has feet like an otter. In fact, when scientists from Europe first discovered the platypus, many of them thought it was a hoax. The Greek root, platypous, means "flat-footed."

Example Sentences

Most modern mammals reproduce by giving birth, but a few species, such as the platypus, still retain the older egg-laying trait.

From Science Daily • May 1, 2026

The world has always been fascinated by the platypus.

From BBC • Aug. 2, 2025

One of the most striking of the new monotremes, Opalios splendens, retains characteristics of the earliest known monotremes, but also some that foreshadow adaptations in the living monotremes, the echidnas and platypus.

From Science Daily • May 27, 2024

Bjorkstrand may have led Columbus in goals for two consecutive years before coming to Seattle, but this was like being the world’s prettiest platypus.

From Seattle Times • May 1, 2024

The boys dived under tables just as the double doors and the brick wall they were mounted to exploded inward, destroyed by the force of the giant, furry platypus beast barreling inside.

From "The Last Last-Day-of-Summer" by Lamar Giles