Welding testing can be divided into destructive testing and non-destructive testing. Destructive testing results in permanent damage to the raw materials or products under test, such as bending test. Non-destructive testing does not damage the raw materials under test. NDT is a widely used non-destructive testing method. NDT is to test raw materials and products through physical and chemical techniques on the premise of not damaging the subjects under test, thus evaluating the quality level and safety degree of the subjects under test. This course will cover the terminology involved in NDT of welded joints, with a focus on four NDT terms such as ultrasonic testing and radiographic testing.