The interconnected conceptual areas of teacher knowledge and teacher beliefs (included by some authors under the rubric of teacher cognition) have been debated in the field of language education intensively for the last two decades, during which time the terminology used in the discussions has been interpreted in a variety of different ways. However, there have been limited attempts to study the way in which teacher knowledge and beliefs develop in specific cases of language teaching methodology: one area of that has not been studied is that of knowledge/beliefs of communicativeness in language teaching. This paper argues that the conceptual area referred to by the above term is multi-dimensional and dynamic. It first develops a framework which focuses specifically on two of these dimensions, a personal-impersonal dimension, and a theoretical-practical dimension. It then examines the interaction between these two dimensions in the specific case of the knowledge of communicative language teaching of six Turkish teachers of English, using the term "understandings" to refer to this dynamic phenomenon. (Contains 3 figures.)