What does the term 'trisomy' specifically refer to?

The term 'trisomy' specifically refers to the presence of three copies of a particular chromosome instead of the usual two copies that are typically found in a diploid organism. This condition can lead to various genetic disorders, depending on which chromosome is affected. For instance, trisomy 21, also known as Down syndrome, occurs when there are three copies of chromosome 21. This additional genetic material results in distinct physical features and an increased risk of certain health issues. The other options describe different chromosomal conditions, such as monosomy (lacking a chromosome) or normal chromosomal setups, which do not relate to the concept of trisomy.