This book compiles original studies investigating crosslinguistic child phonological development in typical and atypical settings, that is, protolanguage phonology. The chapters address topics and issues not widely or exhaustively reported in the literature, such as research on under-represented languages and foci of interest, as well as information that has remained little-known to the field. It documents recent developments on typically developing populations, and atypical developmental speech in children with autism, developmental language disorder affecting speech, childhood apraxia of speech, phonological assessment and intervention, phonological awareness in (a)typical contexts affecting literacy, and motor speech analysis in speech sound disorders. The book will be of interest to linguists and academic researchers, as well as postgraduate students who are investigating child language acquisition in monolingual settings.