1 Introduction 1.1 What Is Second Language Acquisition 1.1.1 Defining Second Language Acquisition 1.1.2 Second Language Aequisition/SLA/L2 Acquisition vs Second/Foreign Language Learning 1.1.3 L1 vs. L2/Target Language/Foreign Language/Additional Language 1.1.4 Naturalistic vs. Instructed Learning/Learners 1.1.5 Acquisition vs. Learning 1.2 The Goals and Scopes of Second Language Acquisition 1.3 The Development of Second Language Acquisition 1.4 The Interdisciplinary Feature of Second Language Acquisition 2 An Overview of the Theories in Second Language Acquisition 2.1 What Is a Theory 2.2 What Makes a Good Theory 2.3 The Classifications of Theories in Second Language Acquisition 2.4 The Ten Observations in Second Language Acquisition 3 Some Key Issues in Second Language Acquisition 3.1 Contrastive Analysis (CA) 3.2 Error Analysis (EA) 3.2.1 The Significance of Laarners Errors 3.2.2 The Procedures in Conducting EA 3.2.3 The Limitations of Error Analysis 3.2.4 A New Direction in Error Analysis 3.3 Interlanguage (IL) 3.3.1 Defining Interlanguage 3.3.2 The Central Processes in Second Language Acquisition 3.3.3 The Characteristics of Interlanguage 3.3.4 The Evaluation of Interlanguage Research 3.4 Transfer 3.4.1 The Definition of Transfer 3.4.2 Different Explanations on Transfer 3.4.3 The Identification of Transfer 3.4.4 The Extent of Transfer 3.4.5 The Constraints on Transfer 3.5 Fossilization 3.5.1 Defining Fossilization 3.5.2 Explanations for Fossilization 3.5.3 The Five Key Issues in Fossilization 3.5.4 Data and Elicitation Measures in Fossilization Research 3.6 The "Comparative Fallacy" in Second Language Acquisition 4 Linguistic Perspective of Second Language Acquisition 4.1 Universal Grammar and Second Language Acquisition 4.1.1 The Poverty of the Stimulus 4.1.2 What Does UG Consist of 4.1.3 Universal Grammar and Second Language Acquisition 4.1.4 The Evaluation of Universal Grammar-based Approaches to Second Language Acquisition 4.2 The Monitor Theory (MT) 4.2.1 The Five Hypotheses in the Monitor Theory 4.2.2 The Evaluation of the Monitor Theory 5 Social Perspective of Second Language Acquisition 5.1 The Socio-educational Model 5.1.1 A Description of the Socio-educational Model 5.1.2 Distinguishing Integrative and Instrumental Motivations 5.1.3 The Attitude Motivation Test Battery (AMTB) 5.1.4 The Evaluation of the Soeio-educational Model 5.2 The Acculturation Model 5.2.1 A Description of Acculturation Model 5.2.2 Stimulus Appraisal Dimensions 5.2.3 The Evaluation of Acculturation Model 5.3 Sociocuhural Theory (SCT) 5.3.1 A General Introduction of Sociocultural Theory 5.3.2 The Applications of Sociocultural Theory in SLA 5.3.3 Zone of Proximal Development (ZPD) 5.3.4 ZPD-related L2 Research 5.3.5 Data Elicitation Methods in SCT 5.3.6 The Evaluation of SCT-related Research 6 Cognitive Perspectives in Second Language Acquisition 6.1 An Overview of Cognitive Theories of Second Language Acquisition 6.2 Implicit and Explicit L2 Knowledge in Second Language Acquisition 6.2.1 Distinguishing Implicit and Explicit Knowledge 6.2.2 Three Interface Hypotheses 6.2.3 The Measurement of Implicit and Explicit Knowledge 6.3 Information Processing Model 6.3.1 A General Introduction to Information Processing Model 6.3.2 The Evaluation of Information Processing Model 6.4 Connectionism and SLA 6.4.1 The Working Mechanisms in Connectionism 6.4.2 Connectionism in Second Language Acquisition 6.4.3 The Evaluation of Connectionism in SLA 6.5 The Competition Model 6.5.1 A General Introduction to the Competition Model 6.5.2 Competition Model in Second Language Acquisition 6.5.3 The Evaluation of the Competition Model 6.6 Processability Theory 6.6.1 A General Introduction to the PT 6.6.2 The Developmental Hierarchy in PT ard Second Language Acquisition 6.6.3 The Evaluation of PT 6.7 Emergentism 6.7.1 Emergentism in Second Language Acquisition 6.7.2 The Research Methodologies in Emergentism 6.7.3 The Evaluation of Emergentism 6.8 Complexity Theory/Dynamic Systems Theory(CT/DST) 6.8.1 The Terminology Issue 6.8.2 The Basic Aspects of DST 6.8.3 The Reconceptualization of SLA from the Perspective of DST 6.8.4 The Paradigmatic Changes Brought by DST 6.8.5 Research Methodologies in DST 6.8.6 The Evaluation of DST-related Research 6.9 Theories of Interlanguage Development 6.9.1 Different Perspectives on Interlanguage Development 6.9.2 Indexes for Measuring Development 6.9.3 Variability in Development 6.9.4 A Comparison of the Developmental Theories 7 Individual Differences in Second Language Acquisition 7.1 An Overview of Individual Difference Research 7.2 Age 7.2.1 Critical Period Hypothesis (CPH) 7.2.2 The Controversies in Age-related Studies 7.2.3 The Age-related Effects on L2 Acquisition 7.2.4 Explanations for Age-related Effects 7.2.5 Pedagogical Implications 7.3 Motivation 7.3.1 The Developmental Phases in Motivational Research 7.3.2 Key Constructs and Models 7.3.3 The Shift in Methodology and Future Directions 7.3.4 Pedagogical Implications 7.4 Language Learning Strategies (LLS) 7.4.1 Definitions of Language Learning Strategies 7.4.2 Theoretical Basis for Language Learning Strategies 7.4.3 Classifications of Language Learning Strategies 7.4.4 Methodologies and Assessments in Language Learning Strategies 7.4.5 Influential Factors in Language Learning Strategies 7.4.6 The Teachability of Strategies 7.4.7 The Evaluation of Strategy Research 8 English as a Lingua Franca (ELF) and Second Language Acquisition 8.1 The New Perspectives on the English Language 8.2 Defining ELF 8.3 Kaehrus Three Concentric Circles of English 8.4 The Paradigm Shift of English under ELF 8.5 ELF-informed English Teaching 8.6 The Evaluation of ELF-informed Pedagogy 9 Epilogue 9.1 The Disciplinary Status of Second Language Acquisition 9.2 The Future Directions of Second Language Acquisition References