Definition for Codominance
From Biology Forums Dictionary
1) The phenomenon in which a single individual expresses both alleles.
2) In genetics, codominance is a phenomenon in which a single gene has more than one dominant allele. An individual who is heterozygous for two codominant alleles will express the phenotypes associated with both alleles.
Codominance and incomplete or semidominance are not the same thing. For example, in some plant species, white and red spotted flowers may be the product of codominance between the red allele for the gene and the white allele for the gene (co-dominance on the pigment level, no dominance on the color level), or the result of one allele that produces the usual amount of red pigment and another non-functional allele that produces no pigment, so as to produce a dilute, intermediate pink color (no dominance at either level).