Final answer:
The minor scale is characterized by a lowered third degree, which gives it a somber and serious quality, different from the brighter sounding major scale.
Step-by-step explanation:
The characteristic that defines the minor scale is that it has a lowered third degree compared to the major scale. This interval is what gives minor scales their distinctively somber, sad or serious quality. Unlike the major mode, which tends to sound more upbeat and happy, the minor mode has a different emotional quality due to this alteration. Minor scales do not necessarily always begin on the note F—that's a feature of a specific minor scale (F minor). Neither do they sound the same as the major mode, as the difference in intervals, primarily the third, provides each with its unique character. Lastly, the minor scale is not made entirely of half steps; it follows a pattern of whole and half steps, which distinguishes it from chromatic scales that are made of half steps only.