fil·ial \ˈfilēəl also -lyəl\adjective Etymology: Middle English, from Late Latin filialis, from Latin filius son + -alis -al — more at feminine 1.: of or relating to a son or daughter; especially: becoming to a child in relation to his parents < filial obedience > 2.: bearing or assuming the relation of a child or offspring • fil·ial·ly\-ēəlē, -yəlē, -li\adverb • fil·ial·ness\-əlnə̇s\noun-es