In this paper, we provide an elaboration of the notion of mathematical structure – a term agreed upon as valuable but difficult to define. We pull apart the terminology surrounding the notion of structure in mathematics: relationship, generalising/generalisation and properties, and offer an architecture of structure that distinguishes and connects these terms. The terminology is then applied to teaching and learning phenomena related to multiplicative reasoning, illustrating how the demarcation of terms can offer a more precise language of description of learning about structure. We present ‘formatting activity’ as a key pedagogic action for accomplishing a focus on structure in teaching.