A recessive trait appears in an organism only when both alleles for that trait are recessive.

Here's a breakdown:

* Alleles: Different versions of a gene.

* Recessive trait: A trait that only shows up if an organism inherits two copies of the recessive allele.

Think of it like this:

* Dominant trait: Like a loud voice that overshadows a quieter one.

* Recessive trait: Like a quiet voice that can only be heard if there's no loud voice to drown it out.

Let's use a classic example: eye color.

* Brown eyes: Usually dominant (let's say 'B')

* Blue eyes: Usually recessive (let's say 'b')

Here are the possibilities:

* BB: Brown eyes (dominant)

* Bb: Brown eyes (dominant)

* bb: Blue eyes (recessive, both alleles are recessive)

So, a person will only have blue eyes if they inherit two copies of the recessive allele ('b').