aplasia

This term is used exclusively within medical and pathological contexts to describe a congenital or acquired absence of growth. It carries a clinical, neutral tone, focusing on the biological failure of a structure to form rather than the functional failure of an existing organ.

Because it describes a specific medical state of non-development, it is treated as an uncountable noun in most clinical descriptions. It does not typically take a plural form unless referring to multiple distinct types of aplasia across different patient cohorts or organ systems.