The main objective of this paper is to apply the onto-semiotic approach to analyze the mathematical concept of different coordinate systems, as well as some situations and university students' actions related to these coordinate systems. The identification of objects that emerge from the mathematical activity and a first intent to describe an epistemic network that relates to this activity were carried out. Multivariate calculus students' responses to questions involving single and multivariate functions in polar, cylindrical, and spherical coordinates were used to classify semiotic functions that relate the different mathematical objects.Keywords Double and triple integration . Multivariate functions . Spherical and cylindrical coordinates . Semiotic registers . Onto-semiotic approach . Personal-institutional duality 1 Different coordinate systemsThe mathematical notion of different coordinate systems is introduced formally at a precalculus level, with the polar system as the first topological and algebraic example. The emphasis is placed on the geometrical (topological) representation and transformations between systems are introduced as formulas, under the notion of equality (x ¼ r cos q; r ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffi x 2 þ y 2 p , etc.). The polar system is usually revisited as part of the calculus sequence; in single variable calculus, the formula for integration in the polar context is covered, as a means to calculate area. In multivariate calculus, work with polar coordinates, and transformations in general, is performed in the context of multivariable functions. It is in calculus applications that the different systems become more than geometrical representations of curves, some familiar (the circle) and some exotic (the rose of 'so many' petals, the Educ Stud Math (2009) 72:139-160