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.

---

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

---

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.

---

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”

Example Sentences

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

Although the hippocampus showed the strongest connection between volume loss and declining memory, many other areas of the brain were also involved.

From Science Daily • Jan. 14, 2026

This accelerating effect appeared across many brain regions, not just the hippocampus.

From Science Daily • Jan. 14, 2026

For their experiment, the pair identified brain cells in a mouse hippocampus that activated when the animal received a startling shock.

From Los Angeles Times • Dec. 27, 2025

Poseidon must’ve known Tyson was one of the passengers, because one hippocampus was much larger than the other two—just right for carrying a Cyclops.

From "The Sea of Monsters" by Rick Riordan