This is distinct from a phenotype, which is any observable characteristic or trait of a disease, such as morphology, development, biochemical or physiological properties, or behavior, without any implication of a mechanism.
[citation needed] One example is asthma, which is considered to be a syndrome, consisting of a series of endotypes.
It is also preferred when etiology is not unique, because the word disease is normally associated to the cause of the clinical problems.
On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.
In clinical trials and statistics the concepts of homogeneous and heterogeneous populations is important.