oligodactyly

Oligodactyly () is the presence of fewer than five digits (fingers or toes) on a hand or foot.

It is quite often incorrectly called hypodactyly; the Greek prefixes hypo- and hyper- are used for continuous scales (e.g. in hypoglycaemia and hyperthermia), as opposed to discrete or countable scales, where oligo- and poly- should be used (e.g. in oligarchy and polygamy). Oligodactyly is therefore the opposite of polydactyly. Very rare, this medical condition usually has a genetic or familial cause.