Abstract
<jats:title>Abstract</jats:title> <jats:p>Instructed second language acquisition (ISLA) is a discipline that aims to enhance second language (L2) development through systematic manipulation of learning processes and conditions to promote both accuracy and fluency in real‐life communication. While both explicit and implicit instruction are important, balanced attention to meaning and form is crucial to develop both fluent and accurate L2 ability. ISLA, by its nature, assumes that instruction can have influences on L2 development, and empirical evidence supports that L2 instruction is beneficial for L2 learners. In this regard, the main focus of ISLA is to explore different learning processes and conditions that can vary the extent of the effectiveness of L2 instruction. This particularly involves exploring the interplay between various types of L2 instruction and factors that impact the effectiveness. Furthermore, ISLA can occur in any environment where there is a deliberate attempt to systematically manipulate L2 learning experiences. Traditionally limited to formal classroom settings, ISLA now include informal, out‐of‐class contexts, which provide various levels of quantity and quality of L2 input, as well as the opportunities for L2 production. Research suggests that different contextual factors can play critical roles in determining the extent of the effectiveness, resulting in different L2 developmental patterns. Given the strong ties to L2 pedagogy since its inception, the ultimate goal of ISLA research is to inform L2 teaching practice for optimal L2 development. Therefore, practice‐based research and collaborative relationships between researchers and teachers are important to improve practical relevance and transferability of ISLA research.</jats:p>