The trait of an organism that can be masked by the dominant form of a trait is called a recessive trait.

Here's why:

* Dominant Traits: These are expressed even if only one copy of the dominant allele is present. They "mask" the recessive trait.

* Recessive Traits: These are only expressed if two copies of the recessive allele are present. If there's even one dominant allele, the recessive trait won't show.

Example: Brown eyes are dominant over blue eyes.

* A person with one brown eye allele and one blue eye allele will have brown eyes because the brown allele is dominant.

* A person with two blue eye alleles will have blue eyes because they have no dominant brown eye allele to mask the recessive blue eye trait.