Down syndrome and Trisomy

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

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

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