This book contains a wide spectrum of topics organized within a relatively fixed framework of Applied Linguistics theory and practice, revolving around the concepts of stability and variability that capture the dynamic nature of the phenomena characterizing language, learning and teaching. The primary strength of individual chapters lies in the fact that the vast majority report original empirical studies carried out in diverse second/foreign language learning contexts – investigating interesting issues across various nationalities, ages, educational and professional groups of language learners, and teachers. The issues under scrutiny entail the ‘classic’ recurrent topics related to language learning and teaching, such as communicative competence, input, orality and literacy, learner characteristics and strategies, and teacher development – to mention just a few. In addition, ‘recent arrivals,’ to borrow a marketing metaphor, are also present, as the authors consider learning and teaching implications resulting from the status of English as a language of international communication, and discuss related concepts of intercultural competence along with language learners’ identity and creativity. The multilingual and multicultural contributors to the present volume are researchers – foreign and second language learners and teachers themselves – who offer the reader a range of methodological designs that have been successfully used in Applied Linguistics research. The framework of stability and variability suggests that changes leading to progress and development derive from stable foundations that account for the sense of continuity and belonging in applied linguists’ communities of practice.