Where in the human body is the "pollex"?

The word "pollex" is the medical Latin name for the thumb and, therefore, the correct answer to the question is indeed "Hand". The plural of "pollex" is "pollices" and the corresponding adjective for thumb is "pollical". In medical terminology there is a similar special word for the big toe: "hallux".

Some modern European languages have words for "thumb" that are quite close to the medical language, in Italian it is called "pollice", in Catalan it is "polze", and in French it is "pouce".

The term "pollex" is also used in zoology as a term for the similar joint in animals, specifically the first digit of the forelimb of amphibians, reptiles and mammals. In birds, the pollex is the joint which bears the alula or "bastard wing"