Which term describes a major interval that has been lowered by half a step?

A major interval that has been lowered by half a step is described by the term diminished interval. In music theory, intervals are the distance between two notes, and they can be classified as major, minor, perfect, augmented, or diminished based on their size and the number of half steps they encompass.

When a major interval is altered by lowering its pitch by a half step, it transforms into a diminished interval. For example, a major third consists of four half steps. If you lower the upper note of that major third by a half step, you end up with a diminished third, which consists of three half steps. This concept is crucial for understanding harmony, chord constructions, and the relationships between notes within different musical contexts.

Understanding diminished intervals provides insight into how composers create tension and resolution in music, making it a fundamental concept in both theory and composition.