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

Mobilizing stored iron by releasing it from the liver and spleen into the bloodstream and bone marrow. —Ayesha Gulzar, Verywell Health, 14 Jan. 2026

For example, survival rates for myeloma, a bone marrow cancer, jumped from 32% to 62%, liver cancer from 7% to 22% and lung cancer from 15% to 28%. —Sara Moniuszko, USA Today, 14 Jan. 2026

The five-year relative survival rate for myeloma (a type of cancer that affects bone marrow), for instance, nearly doubled between the 1990s and now, jumping from 32 to 62 percent, while liver cancer survival more than tripled from 7 to 22 percent. —Jackie Flynn Mogensen, Scientific American, 13 Jan. 2026

According to court records, a powerful animal tranquilizer known as BAM — a combination of butorphanol, azaperone and medetomidine — was found in Suzanne's bone marrow. —Stepheny Price, FOXNews.com, 12 Jan. 2026

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