What is the term for having two different alleles for a trait?

The term for having two different alleles for a trait is indeed "heterozygous." In genetics, alleles are different versions of a gene that can exist at a particular locus on a chromosome. When an individual inherits two different alleles for a specific trait—one from each parent—this condition is referred to as heterozygous.

For example, if an organism has one allele that codes for blue eyes and another that codes for brown eyes, it is considered heterozygous for the eye color trait. This genetic variability can lead to a range of phenotypic expressions and is a key principle of heredity.

In contrast, the term "homozygous" refers to having two identical alleles for a trait, meaning that both inherited alleles are the same. The terms "dominant" and "recessive" describe the relationship between alleles, where a dominant allele expresses its trait even in the presence of a recessive allele. However, they do not indicate the combination of different alleles, which is the essence of heterozygosity.