Transliteration is the practice of converting a text from one writing system into another in a systematic way. In the library world is it used to transcribe non-Roman characters into Roman alphabet. You will find how to transcribe Hebrew letters into English in Hebrew and Yiddish Transliteration Table. This link is to the scanned text of the 1997 edition of the "ALA-LC Romanization Tables: Transliteration Schemes for Non-Roman Scripts," approved by the Library of Congress and the American Library Association. These tables were developed for use when the consistent transliteration of non-Roman script (e.g. Hebrew) into the Roman alphabet is needed, for example, in order to catalog non-Roman materials.