These words are comparable in denoting a capacity to continue living and to reproduce, either in the biological or medical sense, or figuratively. The distinctions relate chiefly to the particular context in which they are used, although some hints are given by their etymology.

Viable , from the French word vie , means capable of living and developing normally: a viable weed, egg or newborn child. It has been applied also to anything thought of as being able to continue an independent existence, and in this sense has the meaning of workable or practicable: a viable plan or project; a viable arrangement.

Fertile goes back to the Latin ferre , to bear, carry or bring, and means capable of producing or reproducing, whether in a material or figurative sense: a fertile woman; fertile soil; a fertile breed of cattle; a fertile imagination; fertile in ideas; a fertile resourcefulness in the face of difficulties. But note that what is viable is not necessarily fertile : a seed or newborn child is viable but can become fertile only at a certain stage in its own development.

By extension, fecund suggests the actual productivity or yield of any fertile person or thing: a fecund woman, who had 12 children; a fecund crop; fecund with ideas. Fruitful , though often a close synonyms of fecund , carries the idea of something that in and of itself promotes further productivity along similar or related lines.

• A well-fertilized soil is fruitful in crops; Newton’s laws were fruitful for the future development of science; The lecture led to a fruitful discussion.

Prolific is a contraction of a medieval Latin word with the literal meaning of to make offspring or progeny. It is more widely used than fecund or fruitful to emphasize a rapid and abundant production of anything.

• Rabbits are prolific animals; He comes of a prolific stock; Colin Simpson is a prolific writer of a travel books.

Proliferous , having the same root as fertile , is generally restricted to biological and medical contexts: a proliferous growth of cells, buds, branches or new tissue.