What is Pathology - What exactly is atrophy?

​What is Pathology - What exactly is atrophy? 
The term "atrophy" refers to a reduction in the size of cells, tissues, or organs. Because the nucleus and cytoplasm of atrophic cells have reduced in size, they are smaller than normal. Atrophic cell-based tissues and organs are noticeably smaller. They can, however, shrink in size as a result of cell loss. Involution is another term for this type of atrophy, which is usually an age-related, irreversible occurrence.