The Glasgow Coma Scale (GCS) objectively measures a patient's level of consciousness and awareness following acute brain injury or illness. It assesses eye opening, verbal response, and motor response on a scale of 3-15, with lower scores indicating more severe impairment. The GCS allows for standardized communication of a patient's condition and guides management decisions. It has been shown to correlate with patient outcomes, with mortality increasing as GCS scores decrease. The GCS is a core assessment for many clinical guidelines involving trauma, critical illness, and neurological conditions.