This chapter focuses on structure across components (morphemes) within a sign and structure at the "morphological" level. It focuses on isolating the properties of language whose development can withstand wide variations in learning conditions—the "re silient" properties of language. Despite great variability in patterns of child-caretaker communications, virtually all children in all cultures master the language to which they are exposed. The deaf children learning American Sign Language (ASL) from parents with incomplete morphological systems go on to develop sign systems with a complex morphological structure indistinguishable from the morphological systems developed by deaf children learning ASL from parents with complete systems. The chapter demonstrates that the signs themselves were in fact composites of handshape and motion morphemes rather than one unanalyzed whole. It also demonstrates that the corpus of signs David produced can be characterized as a system of handshape and motion morphemes, comparable in broad outline to the handshape and motion system that underlies ASL.