Does 1 + 1 = 2nd? The relations between children's understanding of ordinal position and their arithmetic performance.

•Existing studies on the ordinal-math relation often neglect the role of positional information.•We examined ordinal concepts that are contingent on position rather than magnitude.•Positional ordinality was predictive of 5- and 6-year-olds’ arithmetic performance.•Positional ordinality may support math development by providing organization to the number symbols.