Which term refers to a chromosome configuration with an abnormal number of chromosomes, either too many or too few?

The term that refers to a chromosome configuration with an abnormal number of chromosomes, either too many or too few, is aneuploidy. This condition arises when there is a deviation from the normal diploid number of chromosomes in a cell, often resulting from errors during cell division, such as nondisjunction.

Aneuploidy can lead to various genetic disorders, depending on which chromosomes are affected and whether there is an excess or a deficiency in chromosome number. For example, Down syndrome is caused by an extra copy of chromosome 21, illustrating how aneuploidy can have significant effects on an organism's development and health.

In contrast, euploidy refers to a normal complete set of chromosomes for a species, while polyploidy specifically describes a condition where a cell has more than two complete sets of chromosomes, which is often seen in plants. The term homologous relates to chromosomes that pair during meiosis and share the same structure and gene sequence but does not describe the quantity of chromosomes. Thus, aneuploidy is the correct answer as it specifically addresses the aberrant number of chromosomes.