Concept image and concept definition is an important construct in mathematics education. Its use, however, has been limited to cognitive studies. This article revisits concept image in the context of research on undergraduate students' understanding of the derivative which regards the context of learning as paramount. The literature, mainly on concept image and concept definition, is considered before outlining the research study, the calculus courses and results which inform considerations of concept image. Section 6 addresses three themes: students' developing concept images of the derivative; the relationship between teaching and students' developing concept images; students' developing concept images and their departmental affiliation. The conclusion states that studies of undergraduates' concept images should not ignore their departmental affiliations.