thymus

American

[thahy-muhs] / ˈθaɪ məs /

noun

Anatomy.

plural

thymuses, thymi

a ductless, butterfly-shaped gland lying at the base of the neck, formed mostly of lymphatic tissue and aiding in the production of T cells of the immune system: after puberty, the lymphatic tissue gradually degenerates.

thymus British

/ ˈθaɪməs /

noun

a glandular organ of vertebrates, consisting in man of two lobes situated below the thyroid. In early life it produces lymphocytes and is thought to influence certain immunological responses. It atrophies with age and is almost nonexistent in the adult

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

thymus Scientific

/ thī′məs /

An organ of the lymphatic system located behind the upper sternum (breastbone). T cells (T lymphocytes) develop and mature in the thymus before entering the circulation. In humans, the thymus stops growing in early childhood and gradually shrinks in size through adulthood, resulting in a gradual decline in immune system function.

Etymology

Origin of thymus

1685–95; < New Latin < Greek thýmos warty excrescence, thymus

Vocabulary lists containing thymus

Human Anatomy and Physiology - High School

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

But beginning in early adulthood, the thymus starts to shrink.

From Science Daily • Dec. 29, 2025

Inside the thymus, immature T cells go through a checkpoint process that helps create a diverse set of T cells.

From Science Daily • Dec. 29, 2025

His colleagues had discovered that removing the thymus in mice shortly after birth resulted in their immune systems going haywire and the development of autoimmune diseases.

From The Wall Street Journal • Oct. 6, 2025

In December 2020, UK researchers UCL and the Francis Crick Institute rebuilt a human thymus - an essential organ in the immune system - using human stem cells and a bioengineered scaffold.

From BBC • Sep. 4, 2025

In children under two years of age the thymus gland may extend for some distance into the neck in front of the trachea and carotid vessels, under cover of the depressors of the hyoid bone.

From Manual of Surgery Volume Second: Extremities—Head—Neck. Sixth Edition. by Miles, Alexander

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023