here·in 
/hiɚˈɪn/ adverb
/hiɚˈɪn/ adverb formal 1 : in this book, document, etc.
▪ For an explanation of the abbreviations used herein, see the section entitled “Abbreviations in this Work.” 2 : in this statement, fact, or detail — used to introduce something that is related to the main subject and that is usually followed by an explanation ▪ The company faces more competition every year. Herein lies the challenge. In order to maintain our current standing, we have to increase sales.
▪ For an explanation of the abbreviations used herein, see the section entitled “Abbreviations in this Work.”
