Definition of "henceforth"

henceforth

/hɛnsˈfɔɹθ/

adverb
not comparable
1. (formal, temporal) From now on; from this time on.
  Quotations
  My thanes and kinsmen,/Henceforth be earls, the first that ever Scotland /In such an honour named
  c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene ii]
  Henceforth, you shall be known as Darth...Vader.
  2005, George Lucas, Star Wars Episode III: Revenge of the Sith
2. (in metatextual self-reference) Further within this document.