Trisomy
A trisomy is when there are three copies of a chromosome. Normally in humans there is only two copies of any given chromosome. The most notable condition is Trisomy 21 syndrome which is better known as Down syndrome, a form of developmental genetic disorder.
Trisomy 16 is a cause of spontaneous abortion (miscarriage).
Related pages
Wikimedia Commons has media related to Autosomal trisomies.