Carola Ehret first examines the functions that writing can fulfill in the subject-specific learning process and the requirements associated with it for learners. Her theoretical exploration culminates in the didactic modeling of a systematic development of mathematical writing competence at all levels of subject-specific learning. Insights from writing didactics, metacognition research, and mathematics didactics are interconnected, conceptualizing writing as a subject-related process competence. Finally, an initial empirical outlook is provided within the framework of a study on the initiation of mathematical writing competence.