(ˈ) ̷ ̷| ̷ ̷ adverb
Etymology: Middle English therin, from Old English thǣrin, from thǣr there + in
1. : in or into that place : in or into that thing
the box and the jewels found therein
2. : in that particular : in that respect : in such matter
therein our letters do not well agree — Shakespeare