IPA: /ˌpɒlɪˈdæktɪli/
KK: /pɑːlɪˈdæktɪli/
A condition where a person has more than the usual number of fingers or toes.
The child was born with polydactyly, having six fingers on one hand.
Polydactyly is formed from "poly-" (meaning many) and "dactylos" (meaning fingers or toes). The word describes a condition characterized by having many fingers or toes.
Think of 'many' ('poly-') fingers or toes ('dactylos') to remember that polydactyly refers to having extra digits.