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"Viable" is an adjective which is often translated as "viable", and "feasible" is an adjective which is often translated as "factible". Learn more about the difference between "viable" and "feasible" below.
viable(
vay
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uh
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buhl
)An adjective is a word that describes a noun (e.g., the big dog).
1. (feasible)
a. viable 
While offering free products can attract customers, it's not a viable business plan.Aunque ofrecer productos gratis puede atraer clientes, no es un plan viable de negocios.
feasible(
fi
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zih
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buhl
)An adjective is a word that describes a noun (e.g., the big dog).
1. (workable)
a. factible 
In theory, this is a very good idea, but in practice, it's not feasible.En teoría, esta es una muy buena idea, pero en la práctica, no es factible.
Your proposal sounds very interesting, but, unfortunately, it isn't feasible.Tu propuesta suena muy interesante, pero, desafortunadamente, no es factible.
b. viable 
We must find another way to cut costs; raising taxes is not a feasible alternative.Debemos encontrar otra manera de reducir costos; aumentar los impuestos no es una alternativa viable.