Which term refers to the unique quality or tone of a sound that distinguishes it from others?

The term that describes the unique quality or tone of a sound, distinguishing it from others, is timbre. Timbre refers to the characteristics of a sound that allow our ears to differentiate between different sources of sound, even when they are producing the same pitch and volume. For example, the sound of a piano and a violin playing the same note will differ due to their unique timbres. Timbre encompasses various factors, including harmonic content, overtones, and the way the sound is produced.

Intonation relates to the accuracy of pitch in singing or playing instruments, focusing on how in-tune a musician is with the intended notes. Dynamics refer to the variations in loudness and softness of a sound, influencing the emotional impact of music. Vibrato is a technique involving a slight variation in pitch that adds warmth and expressiveness to a tone, but it does not define the unique quality of the sound itself.

Therefore, the correct choice, timbre, captures that distinctive quality that sets sounds apart from one another.