HEREIN Meaning of HEREIN in English here ‧ in /ˌhɪərˈɪn $ ˌhɪr-/ BrE AmE adverb formal in this place, situation, document etc:the conditions stated hereinHerein lies a problem. ⇨ ↑ therein Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012