Andragogy refers to methods and principles used in adult education. The word comes from the Greek ἀνδρ- andr-, meaning "man", and ἀγωγός agogos, meaning "leader of"; it literally means "leading man", whereas " pedagogy" literally means "leading children". Two primary understandings of "andragogy" exist: The science of understanding (theory) and supporting (practice) lifelong education of adults.