Final answer:
Pitch refers to the relative highness or lowness of a sound and is directly related to the sound wave's frequency.
Step-by-step explanation:
The relative highness or lowness of a sound is called pitch. Pitch perception is directly related to the frequency of the sound waves; it explains why we can tell whether one sound has a different frequency from another. For instance, we can discriminate between two sounds if their frequencies differ by as little as 0.3%. A sound's pitch is a fundamental aspect of its character, often used in the creation of music through combinations of musical notes, such as A-sharp, C, or E-flat.