Viability means in general "capacity for survival" and is more specifically used to mean a capacity for living, developing, or germinating under favorable conditions. The word is especially used in the following contexts:

• viability in pregnancy 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. Generally, this ranges from 20-27 weeks.
• viability in environmental conservation indicates the ability of a conservation target to persist for many generations or over long time periods.
• viability of cells and tissues in experimental biology refers to the extent to which those cells and tissues are living.
• viability in natural selection denotes the fraction of individuals that survive to a given age.
• viability in economic development indicates the ability of benefits to cover costs in development projects.

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