Confusion remains about the concept “nursing science.” Definitions vary, depending on country, context and setting. Even among nurse scholars and scientists there is disagreement about the content and boundaries of nursing science. There is an urgent need for an acceptable definition that can guide nursing knowledge development, education, and practice. In this article, we highlight the problems for the profession of this sort of conceptual ambiguity, arguing that it is an ethical responsibility for the profession to gain clarity about the (...) meaning and apt focus of our knowledge development initiatives. We parse out nursing and science as separate concepts and synthesize from this analysis a simple yet comprehensive definition of nursing science. We propose that this definition is capable of unifying ongoing nursing endeavors and should serve as the basis for evaluating nursing's knowledge development and educational initiatives. (shrink)