bekanntlich
Translation
as is well known, famously, notoriously
Examples
Er ist bekanntlich sehr beschäftigt.
As is well known, he is very busy.
Bekanntlich ist Berlin die Hauptstadt Deutschlands.
As is well known, Berlin is the capital of Germany.
Grammar Patterns
As an introductory adverb: as is well known... Bekanntlich ist heute ein Feiertag.
Similar Words
offensichtlich (obviously), anscheinend (apparently)
Etymology
From 'bekannt' (known) + '-lich' (an adverbial suffix, similar to '-ly'). Literally 'known-ly'.
Memory Tips
Think of it as a more formal way of saying 'as you know'. It's often used to state a fact that the speaker assumes is common knowledge.