Final answer:
The degree to which a character is expressed is known as expressivity. It is different from dominance, which involves allele relationships at a locus, and codominance, where both alleles are equally expressed in the heterozygote.
Step-by-step explanation:
The degree to which a character is expressed is known as expressivity. Expressivity refers to the range of expression of a genetic trait within an organism, which can vary among individuals carrying the same genotype. To illustrate, two plants with the same allele for flower color might display shades ranging from pale to deep coloration due to differences in expressivity.
It is important to differentiate expressivity from terms such as dominance, which describes the relationship between alleles at a single locus and how they mask each other's effects; and codominance, where both alleles for the same characteristic are fully and simultaneously expressed in the heterozygote.