The Model for Improvement is a continuous quality improvement methodology and uses specific terminology.
Action Period: The period of time between Learning Sessions when teams work on improvement in their home organizations. They are supported by the Collaborative Leadership and Faculty, and they are connected to other Collaborative Team Members. 
Change Concept: A general idea, with proven merit and sound scientific or logical foundation, that can stimulate specific ideas for changes that lead to improvement. The adaptation of the change concept to local context is the task of the improvement team.
Charter: A written statement of what is to be accomplished and why, and guidance for carrying out the work. The guidance may include measures, aspects of the system on which to focus initially, boundaries within which the changes are to be developed, recommendations for possible changes, and whether specific results are to be expected from the improvement efforts. 
Collaborative: A time-limited effort (usually six to 12 months) of multiple organizations who come together with faculty to learn about and to create improved processes in a specific topic area. The expectation is that the teams share expertise and data so that "Everyone learns, everyone teaches." 
- Plan - a specific planning phase;
- Do - a time to try the change and observe what happens;
- Study - an analysis of the results of the trial; and
- Act - devising next steps based on the analysis.
This PDSA cycle will naturally lead to the Plan component of a subsequent cycle. 
Early Adopter: In the improvement process, the opinion leader within the organization who brings in new ideas from the outside, tries them, and uses experiences with positive results to persuade others in the organization to adopt the successful changes. 
Early Majority/Late Majority: The individuals in the organization who will adopt a change only after it is tested by an early adopter (early majority) or after the majority of the organization is already using the change (late majority). 
- Institute for Healthcare Improvement, How to Improve - Improvement Methods. Available at: http://www.ihi.org/IHI/Topics/Improvement/ImprovementMethods/HowToImprove/.
- Nolan TW, Schall MW. Reducing Delays and Waiting Times Throughout the Healthcare System. Boston, MA. Institute for Healthcare Improvement, 1996.