*We asked #bigmathoff competitor Lucy Rycroft-Smith to tell us a little about her latest project – **CM **Define** It**, an app aiming to collect and define mathematical vocabulary, which launches today.*

When you teach mathematical vocabulary, how do you define its meaning?

Are you exact, choosing your words specifically? Do you give a written definition? Do you give multiple explanations? Do you use diagrams? Metaphors? Connect to previous vocabulary?

As part of our work at Cambridge, creating a Framework for mathematics learning, we are creating a network of semantic links across nodes in our mathematical layer – and we initially thought we could just import a mathematical glossary from somewhere else to populate this. But we found so many inconsistencies, technical errors, and definition loops in many existing glossaries that we decided to make an app to ask the mathematical community what they thought, with the aim of developing a crowdsourced, multi-layered collage which takes into account different layers of mathematical experience.