What is the singular form of phalanges?

The singular form of "phalanges," which refers to the bones in the fingers and toes, is "phalanx." This term is derived from Greek, where "phalanx" denotes a single bone in the digit, while "phalanges" is the plural form used to describe multiple bones across the fingers or toes. Understanding that "phalanges" is the plural allows for the recognition that its singular counterpart must be "phalanx."

The other options do not accurately represent the singular form of the term. "Phalange" does not conform to standard anatomical terminology, whereas "phalanxus" and "phalangium" are not officially recognized terms in the context of anatomy. Thus, "phalanx" is the correct term when referring to an individual bone among the digits.