The Six Sigma process improvement methodology defines the DMAIC and DMADV acronyms as follows.

DMAIC stands for Define, Measure, Analyze, Improve, Control.  These 5 steps are used for improvement of existing processes to identify a candidate process, understand its current state of effectiveness, improve on the process, and manage its continued performance.  This is described in more details under What is Six Sigma

DMADV stands for Define, Measure, Analyze, Design, Verify.  These 5 steps are used when a process doesn’t yet exist and needs to be designed to ensure it will meet customer specifications.  It is also intended to be used when an existing process cannot be improved enough to bring it to within customer specifications and needs to be completely redesigned.

So, in short, what’s the difference? Well, not much.  The DMAIC and DMADV stages are really pretty much the same.  However, the descriptions of each stage vary slightly due to the different contexts in which they are viewed; that is to say whether it is viewed within the context of an existing process intended to perform within pre-established thresholds, or within the context of a new process intended to meet the quantifiable and measurable goals of the customer.

• Define – Define the project goals and customer needs
  
• Measure – Quantify the customers’ needs so the process can be designed to objective standards
  
• Analyze – Analyze the possible options that will meet the customers’ the customers’ needs
  
• Design – Design the new process to meet the quantifiable need of the customer
  
• Verify – Verify the designed process and its ability to meet the customer needs