Final answer:
The interval between any note and its nearest neighbor with the same letter name is called an octave, which spans eight diatonic scale degrees.
Step-by-step explanation:
The interval between any note and its nearest neighbor with the same letter name is called an octave. An octave is a musical interval spanning eight diatonic scale degrees. The two notes at either end of an octave have the same letter name and are considered to be in unison when played together, which means they sound very similar, although one is higher in pitch. For example, if you start on a C note and move up to the next C note, you have moved up an octave. It is also worth noting that a unison (B) refers to two or more musical parts sounding the same pitch or at an octave interval, a third (C) spans three diatonic scale degrees, and a fifth (D) spans five. However, in the context of this question, an octave is the correct answer.