Last time in part two, we built on the stave, time signatures and note types of part one by adding key signatures and major scale construction. If you missed it or need a refresher, you can check out part two here.
This time, we'll be looking at scale degrees, intervals and triads.
Intervals
An interval is a way of describing the difference in pitch between two notes. If the two notes are played together, like an A Major 'Power' chord for instance, it is a harmonic interval:

As you can hopefully see, degrees are pretty straightforward. The second degree of the C Major scale is the second note you play when running the through the scale. The seventh degree is the seventh note you play, the fifth is the fifth... you get the picture!
Scale degrees are used to help us orientate ourselves around the scale, and are very important as part of the foundations of western harmony. They are also important as we move on to the next section...
Triads
It may come as no surprise whatsoever for you to learn that a triad is 3 notes played together. The most obvious example of this is a Major chord. C major for instance is simply the notes C, E and G played together. Looking again at the C major scale above, you can see that C, E and G are the root, third and fifth degrees of the C major scale. Any major scale is made by playing the root, third and fifth degrees of the parent scale together. We can also use the intervals to express this by adding that a major scale is made up of the root, major third and perfect fifth.
A minor chord is constructed also from a root, third and fifth of the parent major scale, but the third is flattened by a semi tone, so we have a root, flattened third and fifth in degrees. Alternatively, we have a root, minor third and perfect fifth expressed as intervals.
And that brings part three to a close. In part four, we'll look at some commonly used symbols, musical directions and terms, and have a little quiz to see if you're starting to put all this together.
When you're playing, try to take a moment just to look at what you're doing, and you'll probably start to see it under your fingertips, as well as on these pages.