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

The disease causes blood cells to grow abnormally in the bone marrow. —Bonnie Bolden, USA Today, 18 Aug. 2025

Following blood tests and a bone marrow biopsy, the mother of two was diagnosed with acute lymphoblastic leukemia (ALL). —Becca Longmire, People.com, 10 Aug. 2025

Besides pain medications to relieve symptoms as well as antibiotics to treat infections, hydroxyurea—a bone marrow suppressive agent that decreases red blood cell production—can be used to reduce the frequency of painful episodes. —Joshua P. Cohen, Forbes.com, 2 Aug. 2025

Serbian medical detective story Guardians of the Formula about the first bone marrow transplant during the Cold War years. —Matthew Carey, Deadline, 1 Aug. 2025

Word History

First Known Use

1590, in the meaning defined above

Rhymes for bone marrow

• caballero
• mescalero
• aero
• faro
• garo
• narrow
• pharaoh
• sparrow
• taro
• bolero
• bracero
• estero

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