?This book looks at the development of language skills in Swedish as a second language in young adults, beginning from the first months of their second language instruction and ending after three years of intensive language courses. The focus is on three proficiency dimensions: complexity, accuracy, and fluency, and their interplay at group level and in individual students.

At the beginning of the second language learning process, accuracy, complexity, and fluency are not integrated in the learner's mind and they tend to act in an arbitrary fashion. During second language development, integration of all dimensions proceeds steadily and after three years of learning the discrepancy between different aspects of proficiency is very low. The study traces the mutual impact of each dimension on particular aspects in order to identify four distinct learner profiles. The goal of this book is to provide a platform for further discussion of the dynamics of second language development and the interconnectedness of the systems involved in this development. Iwona Kowal calls for an individual approach to be taken with every learner and for development to be treated as a constant interplay between many factors.