Are these farewells formal?
A dopo
A tra poco
A presto
A domani
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Sign up to join this communityThe forms of salutations you cite are very common and colloquial. They are typically used with friends and people you are familiar with. They are similar to the more internationally known forms such as:
ciao
and
arrivederci.
A few of the above forms are defined by De Mauro Dictionary
1) A dopo , 2) A più tardi, 3) A presto