cognitive decline

This term is primarily used in clinical, medical, and psychological contexts to describe a loss of mental function. It carries a neutral, diagnostic tone, avoiding the stigma associated with more colloquial terms like "senility" or "dementia," although it often serves as a precursor or a symptom of those conditions.

Because it describes a process of deterioration, it is frequently paired with adjectives that specify the rate or severity of the loss, such as "mild," "moderate," "severe," or "rapid." It is treated as an uncountable noun representing a state or a phenomenon rather than a discrete event.