“ALS, or amyotrophic lateral sclerosis, is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord.  Amyotrophic comes from the Greek language. “A” means no. “Myo” refers to muscle.  “Trophic” means nourishment. So, amyotrophic means “no muscle nourishment,” and when a muscle has no nourishment, it atrophies” or wastes away.  Lateral, in ALS, identifies the areas in a person’s spinal cord where portions of the nerve cells that signal and control the muscles are located.  As this area degenerates, it leads to scarring or hardening (“sclerosis”) in the region.”.

ALS Association (https://www.als.org/understanding-als/what-is-als)