This book presents two distinct yet complementary approaches to the bilingualism of children and adults. This comprehensive work provides a valuable resource for parents, educators, and language instructors, helping them adopt a principled and purposeful approach to education.The primary aim of this book is to assist its target audience in understanding and effectively implement- ing both the natural and ap- plied aspects of bilingual- ism. In this way, readers are guided to support language development and the growth of bilingual individuals.