Severity ratings may differ from company to company and from project to project.
But majority of companies have 4 types of severity:
Severity 1. Showstoppers
These types of software bugs don’t permit the application to move ahead. That is why they are also called showstopper errors.
Severity 2. Application persists with severe errors
Application persists operating with these errors, but they can have high implications, which can be more complex to remove.
Severity 3. Application persists with unforeseen results
In this case the application persists but with unforeseen results.
Severity 4. Suggestions
Errors with such severities are suggestions given by the client to improve the application. These types of software bugs have the least priority and are considered at the finish of the project or during the maintenance phase.