Adults return to study mathematics for a range of varied and complex reasons. This article addresses the boundaries and barriers that adult learners of mathematics may have faced in the past, or in the present and the future. Taking into account the impact of our era of rapid technological change, I argue for the importance of developing structural understanding of disciplinary mathematics together with the equally important contextual knowledge and skills necessary for understanding and engaging with mathematics in often vastly different circumstances from the past. The goal is for adult learners to feel confident, socially included, and able to participate in the mathematical activities with which they are confronted over a lifetime.