Source : Webster's Revised Unabridged Dictionary (1913)

Henceforth \Hence`forth"\, adv.
   From this time forward; henceforward.

         I never from thy side henceforth to stray. --Milton.

Source : WordNet®

henceforth
     adv : from this time forth; from now on; "henceforth she will be
           known as Mrs. Smith" [syn: {henceforward}]