This volume can provide new insights into various theoretical issues in prosody concerning the L2 acquisition process and the linguistic systems (prosodic changes and language development processes may give an indication of what is more or less stable in phonological systems, etc.). In addition, the selected papers clearly show how languages may have influenced or may have been influenced by other language varieties (in multilingual situations where different languages are in constant contact with one another, but also in the process of L2 acquisition). In comparison to previous volumes on related topics, which focus in general either on L2 acquisition or on the description and analyses of different varieties of a given language, our volume, by considering both topics in parallel, may provide the possibility to compare and discuss the results, which may shed new light on more far-reaching theoretical questions such as the role of markedness in prosody, the causes of prosodic changes, etc.