Résumé
This paper explores students' conceptions of the parameters m and c in the linear function y = mx+c. The multiple semiotic representations of linear Junctions lead to multiple mathematical and real-world meanings for m and c. The links between these are an important focus of teaching. The paper reports on responses from three classes of 15 year old students to 7 items requiring interpretation of information about a real-world context. Results confirmed that c (in all four aspects) is a conceptually simpler object than m, but identified that it is often omitted from students' verbal and symbolic descriptions, and treated as if it is not an integral part of the function. Interpretations of both c and in were affected by inadequate distinctions between time (the x variable) as a measure or as a duration of one event.