Keywords: know (already), familiarity, familiar
As a Noun
1. The condition of knowing something or someone already because you have met, seen or been told about them. English = familiarity.
As a Verb or Adjective
1. To know something or someone already because you have met, seen or been told about them before. English = (be) familiar with.
1. Used alone in reply to someone who tells you something you know already, especially when you think they should know you know because it is old news.
1. Used at the beginning of a sentence to introduce a new topic of conversation, especially a person or bit of news, which you are sure the person knows about already.