hippocampus

American  

[hip-uh-kam-puhs] / ˌhɪp əˈkæm pəs /

noun

plural

hippocampi

1. Classical Mythology. a fish-tailed horse of the sea that was ridden by the sea gods.

2. Anatomy. an enfolding of cerebral cortex into the lateral fissure of a cerebral hemisphere, having a major role in learning, emotion, and memory, and named for the seahorse shape of its cross section.

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hippocampus British  

/ ˌhɪpəʊˈkæmpəs /

noun

1. a mythological sea creature with the forelegs of a horse and the tail of a fish

2. any marine teleost fish of the genus Hippocampus, having a horselike head See sea horse

3. an area of cerebral cortex that forms a ridge in the floor of the lateral ventricle of the brain, which in cross section has the shape of a sea horse. It functions as part of the limbic system

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hippocampus Scientific  

/ hĭp′ə-kăm′pəs /

plural

hippocampi

1. A convoluted, seahorse-shaped structure in the cerebral cortex of the temporal lobe of the brain, composed of two gyri with white matter above gray matter. It forms part of the limbic system and is involved in the processing of emotions and memory.

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Other Word Forms

• hippocampal
  adjective

Etymology

Origin of hippocampus

First recorded in 1575–80; from Latin hippocampus, hippocampos, from Greek hippókampos, equivalent to hippo- hippo- + kámpos “sea monster”

Explanation

A hippocampus is a complex neural structure that's part of the brain. Your brain has two hippocampi, and they're important for memories and emotions. This word has a complex history. Originally, it meant a seahorse, and it has also meant a small fish that resembles a seahorse. That resemblance is why the brain structures known as the hippocampus major and hippocampus minor have that name: they look kind of like seahorses too. The hippocampi are found on the floor of your brain's ventricles, and they are vital to feeling and remembering. Without your hippocampi, you wouldn't be who you are.

Example Sentences

In older mice, higher levels of the protein slowed cellular metabolism in the hippocampus.

From Science Daily • Apr. 5, 2026

At the same time, they had fewer connections between neurons in the hippocampus and performed worse on cognitive tests.

From Science Daily • Apr. 5, 2026

As part of their clinical evaluation, electrodes had already been placed in the hippocampus and nearby regions that are critical for memory.

From Science Daily • Mar. 24, 2026

Participants whose vascular indicators more closely resembled those of cognitively healthy adults tended to have lower amyloid levels and a larger hippocampus.

From Science Daily • Feb. 24, 2026

They whisked into the wreckage, and a moment later burst upward in a cloud of bubbles—Grover, Annabeth, and Clarisse each clinging to the neck of a hippocampus.

From "The Sea of Monsters" by Rick Riordan