The term asthenes occurs numerous times in both tannaitic and amoraic literature and is clearly derived from the Greek word ἀσθενὴς (‘without strength’). Saul Lieberman in his book Tosefta Ki-Fshuṭah argues that the term asthenes refers to ‘a person who is weak and sickly by nature’. In my chapter, I will treat the passages in which the word is used, examining how it developed in rabbinic literature and propose a comprehensive understanding of the term.