Heterozygous means having two different versions of a gene (two different alleles) at the same position on a chromosome, one inherited from each parent.

In simple terms, if a gene comes in “version A” and “version a,” a heterozygous person has one of each (Aa), instead of two of the same (AA or aa).

Often, the dominant allele is the one that shows up in your traits, while the other (recessive) allele can be “hidden” but still passed on to children.