- the state of being one of two or more species that are equally dominant in a biotic community: Subalpine fir attains climax dominance or codominance in forests throughout the mountains of western North America.
- the state of being one of two different alleles that are fully expressed in a heterozygous individual: The AB blood group in humans, in which both the A and B alleles are equally expressed, is a classic example of codominance.
