incomplete dominance and codominance both have two alleles in their genotype. Incomplete dominance blends the two traits together while in co-dominance both alleles are clearly shown, they are not blended together. A way you can remember the difference is by thinking about a co-worker, they work together just like CO- dominance, they both start with co. For incomplete dominance, you can remember because neither alleles are complete, so they are incomplete.