Which type of allele configuration is described as having two different alleles for a trait?

The term that describes having two different alleles for a trait is "heterozygous." In genetics, alleles are versions of a gene that can exist at a specific locus on a chromosome. When an organism has two different alleles, for example, one from each parent, it is considered heterozygous for that trait. This configuration often results in the expression of the dominant allele, unless both alleles are recessive.

In contrast, "homozygous" refers to having two identical alleles for a particular trait, meaning both copies of the gene are the same, which does not fit the definition provided. The terms "dihybrid" and "polygenic" describe different genetic concepts. Dihybrid typically refers to the inheritance of two different traits that are controlled by two different genes, while polygenic refers to traits that are controlled by multiple genes, leading to a wide range of phenotypes. Therefore, heterozygous is the correct answer as it specifically reflects the presence of different alleles for the same trait.