英語授課在英語非為母語環境中的增加，已促使學者紛紛研究學生在此環境所面臨的挑戰。然而，前述研究大多採取鎖定單一機構或課程的量化研究，雖強調語言相關的困難，卻忽視英語非為母語的學生以英語學習專業的複雜性。透過van Lier（2000, 2004a, 2004b, 2007, 2008b）語言教育生態學中「可供性」的概念，本質化個案研究探討兩種台灣英語授課環境提供學生學習機會：選擇英語授課修課模式與沉浸式課程模式。研究顯示：雖然學生鮮少了解環境賦予的文化可供性，但他們更常在表現學科興趣、教師的高度期許、與修課彈性上，覺察專業內容與語言之可供性。因此，本文強調個人因素（興趣、修課年級、與背景知識）、情境因素（提供足夠的英語與文化可供性），及兩因素間相互作用，對學生以英語學習專業的重要性。

The proliferation of English-medium instruction (EMI) in nonnative English-speaking (NNES) contexts has compelled researchers to explore the challenges students face in such environments. Mostly quantitative in nature with foci on language-related difficulties in one type of institution or curriculum, these studies obscure the complexity of NNES students' learning of content via English. Through the lens of ＂affordance＂ in van Lier's (2000, 2004a, 2004b, 2007, 2008b) ecology of language education, this qualitative case study examines learning opportunities afforded by two types of EMI contexts in Taiwan: selective EMI courses and an immersion program. Findings showed that despite the limited attention to cultural affordance, more content and language affordances were cognized and acted on in the design where students displayed more interest in subjects, instructors held higher expectations, and flexibility in selection of courses was allowed. As such, this paper underscores the primacy of interests, educational levels, and background knowledge in individual factors; the provision of sufficient English and cultural affordances in contextual factors; and the dynamics between the two in students' learning of content via English.