A chromosome aberration is a deviation from normal. It is a mutation at the chromosomal level, which may be structural or numerical.
Among the numerical (numerical) are euploidies (the chromosomal makeup is multiplied) or aneuploidies, where the numerical aberration involves only one chromosome. An example of a numerical chromosome aberration is:
Down syndrome (trisomy of the 21st chromosome),
Edwards syndrome (trisomy of chromosome 18)
Patau syndrome (trisomy of chromosome 13)