'Herein' definitions:

Definition of 'herein'

(from WordNet)
adverb
In this place or thing or document; "I shall discuss the question herein"

Definition of 'Herein'

From: GCIDE
  • Herein \Here*in"\, adv. [AS. h?rinne.] In this. [1913 Webster]
  • Herein is my Father glorified, that ye bear much fruit. --John xv. 8. [1913 Webster]