Down's syndrome and Trisomy

Down's syndrome noun - A congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation.

Trisomy and Down's syndrome are semantically related. In some cases you can use "Trisomy" instead a noun phrase "Down's syndrome".

Trisomy noun - Chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell.

Down's syndrome and trisomy are semantically related. Sometimes you can replace phrase "Down's syndrome" with "Trisomy", this terms are similar.