What is the difference between defect and defective?
Defect means not meeting a specific requirement or the specification, or failing to achieve a specific customer/client CTQ. A product could have multiple defects. Some of these defects might not even be noticeable by the client. These defects do not functionally affect the performance of the product, still these are defects because it does not meet the specification requirement of the producer.
Defective means the failing of the entire product/service to meet the required criterion. We call a product/service defective because it shows one or more defect(s).
In Six Sigma
In Six Sigma approach the term DPMO (Defects per Million Opportunities) is used to measure the performance of a process. This measurement (DPMO) measures the numbers of defects (or defect opportunities) and not defectives. A defective product can have multiple number of defects.
In Control Charts
If the measurement being plotted is the number of defectives, then you use the p-chart or np-chart.
If the measurement being plotted is the number of defects, then you use c-chart or u-chart.
The number of defectives follow the Binomial Distribution.
The number of defects follow the Poisson Distribution.