This subontology is designed to provide terms to characterize and specify the phenotypic abnormalities defined in the Phenotypic abnormality subontology, with respect to severity, laterality, age of onset, and other aspects.

Note that some of the terms, such as Intellectual disability, have children terms such as Severe intellectual disability that represent precomposed combinations of modifiers and phenotypic abnormality terms. This done where the medical community commonly uses these terms with a fixed meaning (for instance, the Intellectual disability terms are used with specific IQ ranges). For computational reasoning, the semantics are intended to be the same as if there was a combination of the phenotype term and the clinical modifier term.