Hereinafter and Then

Hereinafter adverb - In a subsequent part of this document or statement or matter etc..

Then and hereinafter are semantically related in moreover topic. In some cases you can use "Then" instead an adverb "Hereinafter", when it comes to topics like therefore.

Then adverb - In addition to what has been said.

Hereinafter and then are semantically related in moreover topic. You can use "Hereinafter" instead an adverb "Then".