Sincethepublicationofmylecturenotes,FunctionalDifferentialEquationsintheAppliedMathematicalSciencesseries,manynewdevelopmentshaveoccurred.Asaconsequence,itwasdecidednottomakeafewcorrectionsandadditionsforasecondeditionofthosenotes,buttopresentamorecomprehensivetheory.Thepresentworkattemptstoconsolidatethoseelementsofthetheorywhichhavestabilizedandalsotoincluderecentdirectionsofresearch.