Henceforth vs Thereinafter - What's the difference?

As adverbs the difference between henceforth and thereinafter

is that henceforth is (formal) from now on; from this time on while thereinafter is in the following part (of this document or speech).

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(formal) From now on; from this time on.

* William Shakespeare, Macbeth , Act I, scene II:

My thanes and kinsmen,/'Henceforth be earls, the first that ever Scotland /In such an honour named

I will try to do a better job, henceforth , now that I know the proper technique!

* henceforward

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in the following part (of this document or speech)