Viability means in general "Capacity for survival" and is more specific used to mean:

• In the context of pregnancy, viability refers to either:
  • an early stage pregnancy that has a chance of reaching full-term and a live birth (as opposed to, for example, an ectopic pregnancy); or
  • the shortest length of pregnancy after which a child born prematurely has a chance of survival.
• In an environmental conservation context, viability indicates the ability of a conservation target to persist for many generations or over long time periods.
• In the context of experimental biology, viability of cells and tissues refers to the extent to which those cells and tissues are living.
• In the context of natural selection, the fraction of individuals that survives to a given age.