The names of the intervals, such as Major 2nd, Minor 2nd, etc., come from
Scales.
A scale is a series of closely spaced notes in ascending or descending order.
The most common scale is called the C Major Scale.
The Major Scale acts as a ruler. On a normal ruler the numbers are evenly spaced.
In a Major Scale, however, the numbers are not evenly spaced.
A Major Scale is made of two different units called a Half Step and a Whole Step.
A Half step is the same size as a Minor 2nd, or a Semitone.
A Whole step is the same size as a Major 2nd, and is equal to two Half Steps.
A Major Scale is made of an unequal pattern of Whole Steps and Half Steps like this:
Whole Whole Half, Whole Whole Whole Half.
This scale is so common that it is actually built in to most instruments, including the piano.
Any time you play the white keys in ascending order starting on C, you have a C major scale.
On the guitar you can think of each key you see here as 1 fret.
Please press the Exercise button below.