1. The ability to live; capable of normal growth and development: After the mother cat had her six kittens, Jane wondered about the viability of the last and tiniest one.
2. The quality of having a practical and plausible chance of success: The viability of Susan inviting all of her 15 friends to her birthday party depended on her parents allowing her to ask them.
3. The capacity of working well and favorably: The viability of the shop to survive depended on the number of people buying the items offered, keeping on top of the operating costs of the shop and personnel, and not making any debts.

The capacity of a fetus to survive outside the womb following birth: Fetal viability is dependent mainly on the organ maturity or development of the baby and of the environmental circumstances.

Historically, a fetus was thought to be capable of living after the 20th gestational week. But, in reality. a baby does not have much of a chance to survive when it is born before 24 completed weeks of gestation.