As part of the wider BR-UK consortia, The Behavioural Concepts Group (BCG) has begun work to develop clear consensual definitions of key concepts in behavioural research and BR-UK, with the aim of developing a broad consensual framework about influences on behaviour and how behaviour changes. This group has eight members and has developed a protocol for defining key terms and concepts. This includes the group reviewing and agreeing on characteristics of good core and ontological definitions and conducting a consultation amongst the BR-UK team initially on the following terms: behaviour; behaviour change; research; and leadership. BCG members will work alongside the ontology demonstration project team (Demo project 3) to review the definitions. When the BR-UK reaches a consensus, members from the BR-UK stakeholder network and the ISAB will be invited to consider them further.