What term expresses sorrow or is characterized as melancholy?

The term that best expresses sorrow or is characterized as melancholy is "plaintive." This word is often used to describe sounds, tones, or expressions that convey sadness or a mournful quality. For example, plaintive melodies or plaintive cries evoke feelings of sorrow and longing, effectively capturing the essence of a melancholic mood.

In contrast, the other terms listed do not directly convey sorrow or melancholy. "Plumb" relates more to measurement or depth rather than emotional expression. "Peculiar" refers to something that is strange or unusual, lacking any intrinsic association with sadness. "Pallor," while it denotes paleness, typically associated with illness or shock, does not inherently express emotional sorrow. Therefore, "plaintive" stands out as the term that accurately encapsulates sorrowful or mournful characteristics.