Due to the embeddedness of digital technologies in mathematics education of today, we often see examples of students simultaneously using their mathematical competencies and digital competencies. In relevant literature, however, these are not seen as a connected whole. Based on reviewing existing competency frameworks, both mathematical and digital, and by exploring an empirical example, this article addresses the question of how to think about and understand a combined "mathematical digital competency" (MDC). In doing so, the article relies on the two theoretical frameworks of the instrumental approach and conceptual fields to "bridge" the mathematical and digital competency descriptions.