As nouns the difference between carpel and carpal

is that carpel is one of the individual female reproductive organs in a flower. A carpel is composed of an ovary, a style, and a stigma, although some flowers have carpels without a distinct style. In origin, carpels are leaves (megasporophylls) that have evolved to enclose the ovules. The term pistil is sometimes used to refer to a single carpel or to several carpels fused together while carpal is any of the eight bones of the wrist (carpus).

As an adjective carpal is

of or pertaining to the carpus.