hydra

American  

[hahy-druh] / ˈhaɪ drə /

noun

plural

hydras, hydrae,

genitive

Hydrae

1. Classical Mythology. Often Hydra a water or marsh serpent with nine heads, each of which, if cut off, grew back as two; Hercules killed this serpent by cauterizing the necks as he cut off the heads.

2. any freshwater polyp of the genus Hydra and related genera, having a cylindrical body with a ring of tentacles surrounding the mouth, and usually living attached to rocks, plants, etc., but also capable of detaching and floating in the water.

3. a persistent or many-sided problem that presents new obstacles as soon as one aspect is solved.

4. (initial capital letter) the Sea Serpent, a large southern constellation extending through 90° of the sky, being the longest of all constellations.

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Hydra ¹ British  

/ ˈhaɪdrə /

noun

1. a very long faint constellation lying mainly in the S hemisphere and extending from near Virgo to Cancer

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hydra ² British  

/ ˈhaɪdrə /

noun

1. any solitary freshwater hydroid coelenterate of the genus Hydra, in which the body is a slender polyp with tentacles around the mouth

2. a persistent trouble or evil

   the hydra of the Irish problem

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Hydra ³ British  

/ ˈhaɪdrə /

noun

1. Greek myth a monster with nine heads, each of which, when struck off, was replaced by two new ones

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hydra Scientific  

/ hī′drə /

plural

hydras

1. See under hydroid

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Etymology

Origin of hydra

First recorded in 1325–75; from Latin hydra, from Greek hýdrā “water serpent” (replacing Middle English ydre, from Middle French, from Latin); see otter

Example Sentences

Samar shares the popular view that for every senior official "they've reportedly assigned three to seven successors. Like a hydra - you cut one head off, another grows back. They won't surrender any time soon."

From BBC • Mar. 25, 2026

"In 20 years, and despite the resolute efforts of our police officers, gendarmes, judges, teachers and elected officials, the antisemitic hydra has kept advancing," he said.

From Barron's • Feb. 13, 2026

“It’s like a hydra, like a three-headed monster!” she says with a hearty laugh.

From Los Angeles Times • Jan. 22, 2025

This suggests that evolution plays around with these chemical pathways, altering them over the hundreds of millions of years since the hydra and human lineages diverged from each other on the evolutionary tree.

From Scientific American • Jun. 16, 2023

The sword wasn’t designed for that, but the Celestial bronze blade sliced through the chains suspending the hydra.

From "The Mark of Athena" by Rick Riordan

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