Learn German: Der regelmäßige Umgang ist erwiesenermaßen wichtig. - Regular contact is demonstrably important.

It is built from the past participle erwiesen (from erweisen, meaning to prove or establish), the linking element -er-, and the suffix -maßen (meaning to a measure or extent). Together, it forms an adverb expressing an established fact, translating to "as has been proven" or "demonstrably".

Could I just say ist erwiesen wichtig without the -ermaßen ending?

No, that would sound unnatural. When you want to use a participle like erwiesen as an adverb that comments on the truth of the whole statement, you need the -ermaßen suffix. Without it, erwiesen functions mainly as a normal adjective, as in eine erwiesene Tatsache (a proven fact).

The word Umgang often means "handling." How does it translate to "contact" in this context?

Umgang is a versatile noun. While it does refer to how you handle objects or situations, in interpersonal contexts it means socializing, interaction, or contact with people. In this sentence, der regelmäßige Umgang refers to keeping in regular touch with someone.

Why does regelmäßige end in -e here instead of -er, given that Umgang is a masculine noun?