DNA damaging agents and radiation, cytotoxins and anti-cancer drugs, telomere erosion and cytokines, culture shock and mitogenic stimuli, oncogenes and tumor suppressors can induce both cell cycle arrest and cellular senescence. Due to this semi-coincidence, senescence is confused with cell cycle arrest, or even more misleadingly, with growth inhibition. With such misconceptions, cellular senescence cannot be linked to organismal aging. Also, the relation between cancer and senescence is distorted. Here I discuss why the link between arrest and senescence is semi-coincidental and how senescence is related to aging and cancer.