Final answer:
An organism with identical alleles for a trait is described as homozygous, which can be either homozygous dominant or homozygous recessive.
Step-by-step explanation:
When an organism has two identical alleles for a specific trait, the term used to describe it is homozygous. An organism can either be homozygous dominant if both alleles are the dominant type (AA), or homozygous recessive if both alleles are recessive (aa).
Heterozygous refers to having two different alleles (Aa), one dominant and one recessive. In the expression of traits, dominant alleles will mask the presence of recessive alleles in a heterozygous pairing, thereby producing the same phenotype as a homozygous dominant individual. However, the recessive trait will only be visible in the phenotype of a homozygous recessive individual.