In this opening commentary, we highlight the development of the teaching and learning of Chinese as a second or foreign language (CSL/CFL), which has attracted much attention from researchers, language educators, and other stakeholders worldwide. To contribute to this ongoing examination and discussion, this special issue documents the collective efforts of scholars in different educational contexts to review six critical issues in teaching and learning CSL/CFL: learning and instruction of reading Chinese as an additional language, Chinese character teaching and learning, learner identity in CSL/CFL education, teaching and learning Chinese through immersion, technology assisted CSL/CFL teaching and learning, and mobile assisted learning CFL. We contend that all efforts to address these critical issues require constant examination to facilitate further development in CSL/CFL education around the world.

在这篇开场评论中，我们重点介绍了汉语作为第二语言或外语（CSL/CFL）教学和学习的发展，这引起了全球研究人员、语言教育工作者和其他利益相关者的高度关注。为了促进这一正在进行的检验和讨论，本期特刊记录了不同教育背景的学者们的集体努力，回顾了对外汉语教学中的六个关键问题：汉语作为附加语言的阅读学习和指导、汉字教学和学习。学习、CSL/CFL 教育中的学习者身份、沉浸式汉语教学、技术辅助 CSL/CFL 教学以及移动辅助学习 CFL。我们认为，解决这些关键问题的所有努力都需要不断审查，以促进世界各地 CSL/CFL 教育的进一步发展。