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"Constancia" is a noun which is often translated as "perseverance", and "consistencia" is a noun which is often translated as "consistency". Learn more about the difference between "constancia" and "consistencia" below.
la constancia(
kohns
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tahn
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syah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. perseverance 
El éxito viene con constancia y una estricta ética del trabajo.Success comes with perseverance and a strict work ethic.
2. (evidence) (Latin America)
Regionalism used in Latin America: all the countries in South America, Central America, and the Caribbean. Does not include Spain.
la consistencia(
kohn
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sees
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tehn
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syah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (general)
a. consistency 
La masa no tenía la consistencia deseada porque no medimos bien los ingredientes.The dough didn't have the desired consistency because we didn't measure the ingredients accurately.