Ageing as a field of research

The nineteenth entry is o efeito de sobrevivência, and the English term for it is not built on the word a reader reaches for first. « Survival » names the fact of coming through, and it is everywhere: a survival rate, a survival kit, the survival of a species. The distortion this entry names is « survivorship bias », and « survivorship » is a different noun with a different job. It names the standing of the one who is still there rather than the event of lasting, and outside statistics an English reader meets it first in the law of property, where « the right of survivorship » is the rule by which a jointly owned house passes straight to the surviving owner and never goes near the will. Carry that sense across and the statistical term explains itself: a sample made only of what is still standing, with everything that dropped out of it silently absent. Two notes for writing it. « Survival bias » is heard and understood, but « survivorship bias » is the settled form. And biology uses the same stem again in « the survivorship curve », which plots how many of a cohort are left alive at each age.