Several countries currently call the condition myalgic encephalomyelitis, ME/CFS or CFS/ME. Some experts use the terms interchangeably, while others consider one a subgroup of the other.
In the United States, advocates are working to have the name of CFS officially changed to ME/CFS due to the widespread belief that the name CFS trivializes the condition and leads to misperceptions of it. Disagreement over whether encephalomyelitis or encephalopathy is more accurate led to the decision to push for the simple acronym ME.
Myalgic means muscle pain or tenderness. Encephalomyelitis means inflammation of the brain and spinal cord. Encephalopathy means altered brain function and structure caused by diffuse brain disease.