Two different alleles for a trait are called heterozygous.

Here's why:

* Allele: A specific version of a gene.

* Heterozygous: Having two different alleles for a particular gene.

For example, let's say the gene for eye color has two alleles: one for brown eyes (B) and one for blue eyes (b). An individual with one brown eye allele (B) and one blue eye allele (b) would be considered heterozygous for eye color.