An evolutionary biology term referring to any sort of physical or behavioral trait that is presumed to be the result of an expression of an assumed genotype. Evolutionary biologists reason with genotypes and phenotypes, positing that they must exist even though the revelation of the actual mechanics of genetics has greatly complicated the simple Darwinian paradigm.
Phenotypes get very squirrelly when we get to evolutionary psychology, for the same reason that psychology has a replication crisis.