Delirium can be defined as:

Delirium is characterized by a significant disturbance in attention and awareness, often accompanied by a fluctuating course. This means that an individual's ability to focus and engage with their environment can vary over time, leading to periods of confusion and disorientation. The acute onset of these symptoms distinguishes delirium from more chronic conditions.

In contrast to chronic cognitive conditions, delirium is typically temporary and reversible if the underlying cause is addressed. It is not classified as a permanent cognitive decline, which would suggest lasting impairments consistent with disorders such as dementia. Additionally, delirium is not an anxiety disorder, despite the presence of confusion, as it primarily affects attentional processes and consciousness rather than being rooted in anxiety. Understanding delirium's defining characteristics allows for appropriate assessment and intervention, especially in medical settings where timely recognition is crucial for effective treatment.