Incomplete Dominance

Dominant Allele: An allele that expresses its phenotypic effect even when it's paired with a different allele; typically masks the effect of a recessive allele.

Recessive Allele: An allele that only expresses its phenotypic effect when it's paired with an identical recessive allele.

Phenotype: The observable physical properties of an organism; these include the organism's appearance, development, and behavior.