A melodic interval is the distance between two musical notes played in sequence, rather than simultaneously. It is measured in terms of the number of scale degrees between the notes. For example, the interval between the notes C and E is a major third, as there are four half steps between them. Melodic intervals are essential in music composition and analysis, as they help define the character and emotion of a melody. Understanding these intervals allows musicians to create more expressive and varied musical phrases, enhancing the overall listening experience.