A form of programmed cell death (apoptosis) induced in certain cell types when they become detached from their extracellular matrix or from a surface. Epithelial, endothelial, and many other tissue cells depend on continual interchange of signals with neighbouring cells and their immediate environment in order to survive. The absence of such signals following detachment from the matrix normally results in death of the cell. However, when tumour cells detach they resist anoikis, allowing them to migrate to new sites and seed new tumours. Hence understanding this process is key to the effective treatment of various cancers. The term is derived from the Greek word for homelessness.