Which condition involves the complete absence of a limb?

The condition characterized by the complete absence of a limb is complete phocomelia. Phocomelia is a limb deficiency condition that results in the underdevelopment or absence of arms or legs, and when it is described as "complete," it indicates that the entire limb is missing rather than being partially formed or shortened.

In contrast, incomplete phocomelia refers to a situation where some part of the limb may be present, but it is significantly underdeveloped or malformed. Paraxial hemimelia and pre or post axial hemimelia refer to specific types of limb deficiencies, typically involving malformations or incomplete development of limbs rather than the total absence of a limb. Therefore, complete phocomelia is the correct choice as it directly matches the definition of a condition where a limb is entirely missing.