: the layer of vascular connective tissue lining the medullary cavities of bone

Word History

Etymology

New Latin, from end- + Greek osteon bone — more at osseous

First Known Use

circa 1881, in the meaning defined above

Time Traveler
The first known use of endosteum was circa 1881

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Cite this Entry

“Endosteum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/endosteum. Accessed 8 Jul. 2026.

Medical Definition

endosteum

noun
: the layer of vascular connective tissue lining the medullary cavities of bone

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