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"Polite" is an adjective which is often translated as "educado", and "diplomatic" is an adjective which is often translated as "diplomático". Learn more about the difference between "polite" and "diplomatic" below.
polite(
puh
-
layt
)An adjective is a word that describes a noun (e.g., the big dog).
1. (respectful)
a. educado 
The boy was very polite; he didn't misbehave once.El niño fue muy educado; no se portó mal ni una vez.
diplomatic(
dih
-
pluh
-
mah
-
dihk
)An adjective is a word that describes a noun (e.g., the big dog).
a. diplomático 
The new prime minister took a tour of the continent to strengthen diplomatic ties.La nueva primera ministra hizo una gira por el continente para fortalecer vínculos diplomáticos.
2. (tactful)
a. diplomático 
James managed to give his sister a diplomatic explanation of what happened to their dog.James logró darle una explicación diplomática a su hermana de lo que le sucedió a su perro.