di·​en·​ceph·​a·​lon ˌdī-ən-ˈse-fə-ˌlän How to pronounce diencephalon (audio)
-lən How to pronounce diencephalon (audio)
: the posterior subdivision of the forebrain
ˌdī-ən-sə-ˈfa-lik How to pronounce diencephalon (audio)

Example Sentences

Recent Examples on the Web The diencephalon regulates sleep-wake cycles and motor reflexes, while the brain stem controls automatic functions like breathing, blood pressure, heart rate, swallowing and pupil dilation. Adrian Owen, Discover Magazine, 12 Nov. 2017 This gene is involved in brain development and is mostly expressed in a part of the brain called the diencephalon — an area previously found to differ in gay men. Leah Froats, Discover Magazine, 7 Dec. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diencephalon.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


New Latin, from dia- + encephalon

First Known Use

circa 1883, in the meaning defined above

Time Traveler
The first known use of diencephalon was circa 1883

Dictionary Entries Near diencephalon

Cite this Entry

“Diencephalon.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/diencephalon. Accessed 21 Mar. 2023.

Medical Definition


di·​en·​ceph·​a·​lon ˌdī-ən-ˈsef-ə-ˌlän How to pronounce diencephalon (audio) ˌdī-(ˌ)en- How to pronounce diencephalon (audio)
: the posterior subdivision of the forebrain

called also betweenbrain, interbrain

diencephalic adjective
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