What term describes an organism with two different alleles for a trait?

The term used to describe an organism with two different alleles for a trait is "heterozygous." This genetic configuration arises when an individual receives different forms (alleles) of a gene from each parent, resulting in a combination such as one dominant and one recessive allele (e.g., Aa).

Heterozygosity can significantly influence the phenotype, or observable traits, of the organism, often leading to expressions that are indicative of the dominant allele. This concept is fundamental in genetics as it helps to explain variation within a population and the principles of inheritance.

In the context of the other terms, "homozygous" refers to an organism possessing two identical alleles for a trait, thereby indicating a lack of variation at that genetic locus. "Dihybrid" and "monohybrid" refer to the number of traits being studied in a cross, with dihybrid referring to two traits and monohybrid to one trait. These terms do not specifically address the allelic composition of an organism regarding a single trait and thus are not applicable in this scenario.