萎缩为身体部分或是完全的日渐渐消瘦。造成萎缩的原因包含突变(可破坏创建器官的基因)、营养不良、不好的循环系统、失去激素(荷尔蒙)的帮助、失去目标器官的神经支持、超过的细胞凋亡以及缺乏体能锻炼或是组织本身的内在疾病所导致。维持器官或身体一部分的激素和神经输入，在医学名词上称为trophic。Trophic描述组织的营养状况。肌肉Trophic的减少，被称为萎缩。

萎缩为一般组织崩解或是重新吸收的生理学上的过程，牵涉到细胞的凋亡。当萎缩的发生是由于一些疾病则称为物理性的萎缩，有时这是属于正常身体 的稳态(体内平衡)。

Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, excessive amount of apoptosis of cells, and disuse or lack of exercise or disease intrinsic to the tissue itself. In medical practice, hormonal and nerve inputs that maintain an organ or body part are said to have trophic effects. A diminished muscular trophic condition is designated as atrophy.