bone marrow

noun

: a soft highly vascular modified connective tissue that occupies the cavities of most bones and occurs in two forms:
a
: one that is yellowish, consists chiefly of fat cells, and is found especially in the cavities of long bones
b
: one that is reddish, is the chief site of blood cell formation, and occurs in the normal adult in cancellous tissue especially of certain flat bones

called also red marrow

Examples of bone marrow in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Multiple myeloma is a cancer of plasma cells, which are found in bone marrow and are a vital part of the immune system, according to the American Cancer Society. — Chris Jordan, USA Today, 4 Aug. 2026 Its flagship drug is Jakafi, a treatment for rare bone marrow disorders that has carried the company for over a decade. — Josh Brown,sean Russo, CNBC, 3 Aug. 2026 The show is about a 17-year-old from a working-class New Jersey town who wants to become an astronomer but must deal with the harsh realities of daily life, including his half-sister’s need for a bone marrow transplant. — Jessica Gelt, Los Angeles Times, 31 July 2026 The newest example targets acute lymphoblastic leukemia, a fast-growing cancer of the blood and bone marrow. — William A. Haseltine, Forbes.com, 28 July 2026 See All Example Sentences for bone marrow

Word History

First Known Use

1590, in the meaning defined above

Time Traveler
The first known use of bone marrow was in 1590

Rhymes for bone marrow

See All Rhymes for bone marrow

Browse Nearby Words

Bonellia
bone marrow
bonemeal
See all Nearby Words

Cite this Entry

“Bone marrow.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/bone%20marrow. Accessed 5 Aug. 2026.

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Kids Definition

bone marrow

noun
: a soft tissue rich in blood vessels that fills the cavities of most bones and occurs in two forms:
a
: one that is yellowish and fatty and is found especially in long bones (as the femur)
b
: one that is reddish, is the main place where blood cells are formed, and in adults is limited especially to certain flat or short bones (as the ribs)

Medical Definition

bone marrow

noun
: a soft highly vascular modified connective tissue that occupies the cavities and cancellous part of most bones and occurs in two forms:
a
: a whitish or yellowish bone marrow that consists chiefly of fat cells and is found especially in the cavities of the long bones

called also yellow marrow

b
: a reddish bone marrow that contains little fat, is the chief site of red blood cell and blood granulocyte formation, and occurs in the normal adult in cancellous tissue especially of certain flat bones

called also red marrow

More from Merriam-Webster on bone marrow

Britannica.com: Encyclopedia article about bone marrow

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