pineal gland

noun

variants or less commonly pineal or pineal body or pineal organ

: a small, typically cone-shaped structure of the brain that arises from the roof of the third ventricle, is enclosed by the pia mater, and functions primarily as an endocrine gland secreting melatonin

Note: The pineal gland varies in morphological complexity, and in some nonmammalian vertebrates (such as various reptiles) may serve a photoreceptive function.

Examples of pineal gland in a Sentence

Recent Examples on the Web

Melatonin Melatonin is a hormone secreted primarily by the pineal gland (located deep in the brain). —Heather Jones, Verywell Health, 10 Oct. 2025

Melatonin is a natural hormone produced in the body by the brain’s pineal gland which partially controls the sleep-wake cycle. —Ashley J. Dimella, FOXNews.com, 4 Oct. 2025

The smallest organ is the pineal gland, located in the back of the brain. —Scott Lafee, San Diego Union-Tribune, 15 July 2025

This wellness trend is all about, well, maximizing your sleep every night with practices like mouth taping, pineal gland meditation, sleeping in a cold room, and more. —Sherri Gordon, Health, 12 May 2025

Word History

First Known Use

1712, in the meaning defined above

Rhymes for pineal gland

• ampersand
• beforehand
• behindhand
• bottomland
• contraband
• countermand
• dixieland
• fairyland
• fatherland
• firebrand
• hinterland
• motherland

Kids Definition

pineal gland

noun

pi·​ne·​al gland

ˈpī-nē-əl,

pī-ˈnē-

: a small usually cone-shaped part of the brain of most vertebrates that has an eyelike structure in reptiles and produces melatonin especially in response to darkness

called also pineal body

Medical Definition

pineal gland

noun

: a small body that arises from the roof of the third ventricle and is enclosed by the pia mater and that functions primarily as an endocrine gland that produces melatonin

called also pineal, pineal body, pineal organ