Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A congenital disorder, caused by the presence of an extra 21st chromosome, in which the affected person has mild to moderate mental retardation, short stature, and a flattened facial profile. Also called trisomy 21.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Condition caused by a chromosomal excess, whereby the patients bear a certain resemblance to the Mongoloid race, such as a small head and tilted eyelids, and typically have a delay in cognitive ability and physical growth.

from the GNU version of the Collaborative International Dictionary of English

  • n. A congenital disorder caused by an extra chromosome 21 in some or all cells. It causes a variable number and degree of abnormalities, including retarded growth, mental retardation, a short nose, prominent epicanthic folds on the eyelids, a protruding lower lip, and other physical features having varying degrees of deviation from the normal. Called also mongolism, trisomy-21 and trisomy 21 syndrome.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation

Etymologies

After John Langdon Haydon Down (1828-1896), British physician.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Named after John L.H. Langdon-Down (1828-1896), an English physician who described it in the late 1800s. The term was first used in 1961. (Wiktionary)

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