Mathematical orthography comprises knowledge of mathematical symbols and the conventions for combining those symbols. For example, in the expression x3 + 3x, the positions of the symbol "3" in each term dictate its meanings in the expression. To be successful mathematical problem solvers, people need to know these conventional orthographic patterns. In this study, mathematical orthography skills were assessed in an online format for 189 adults using a timed dichotomous symbol-decision task (e.g., are these expressions conventional? (|