The study reviews on the concept of senescence and some important synonymous terms of it. The term ‘Senescence’ has deeper roots than Programmed Cell Death (PCD)’. Senescence can be regarded to occur at microscopic as well as microscopic levels. At microscopic levels, the process is continuous and can be viewed as Programmed cell death’. Thus both PCD and senescence can be viewed as synonyms at cellular level. Senescence is characterized by a number of catabolic processes as protein degradation, nucleic acid and nuclear degradation, lipid peroxidation, disruption of cell membranes etc., but at the same time, it prepares the plant to start the next generation by remobilizing essential nutrients to developing organs which makes it important for the success of subsequent generations. Although true apoptosis has not been found to occur in plants, but some features of it have been implicated to occur in plants. Recent studies have also revealed the differential expression of some genes in plant systems that were earlier found to express during animal cell death. It is therefore to be decided whether the term apoptosis’ will be still restricted to animal systems only. Ageing refers to degenerative changes that occur in all organisms without any reference to death, while senescence refers to the developmental stage at which close to death’ symptoms becomes apparent.