This article examines how adult learners were socialized by one another in the context of content materials in conjunction with the teacher's participation. Based on the premise that second language learning is experiential and emergent and using discourse analysis of students' asynchronous electronic postings and writing assignments together with ethnographic observations, we traced the students' evolving understandings of a culturally rich word, "stereotype", over the course of one semester. We first looked at how the students understood the meaning of "stereotype" in early discussions, then at how these initial understandings changed as the students engaged in social activities in which their stances and identities became relevant, and finally at how these changes were exhibited in later discussions and written essays. Our analysis demonstrates concretely that learning a second language involves the acquisition not only of linguistic forms but also ways of thinking and behaving in new communities of practice.