The distance from the Root to any note is a Quantitive interval.
The distance from any any note to any other is called a qualitive interval.
The interval names are built in half steps and are named after the terms major and minor.As you probably know they run in the order of;
Root
min.2nd
Maj.2nd
m3rd
M3rd
P4th
b5th
P5th
m6th
M6th
m7th
M7
Octave

When you take away all of the Major intervals they become the Major scale R,M2,M3,P4th,P5th,M6th,M7th,Oct.
Leaving behind..m2,m3,b5th,m6th,m7th
So the distance from any min. or Maj. relates to Qualitive or Quantitive.But when you go backwards from say Oct. to m6th.this is called a lowered 5th.
So the distance from Root to any note is a Quana
tive.Any distance from one note to another is Qualitive
Any desending can be considered a lowerd interval

Ryan;
U are correct in saying that 2nd, 3rd, 6th, and 7th are major. 4th, 5th, and 8th (octave) are perfect. But
1 (unison)like 2 instruments playing the same note is also perfect. Intervals are various combinations of half-steps. Changing the intervals
with flats or sharps, changes them from Major and Perfect into minor, diminished and augmented. The entire set of major and perfect intervals are called diatonic intervals. I hope this helps
Black Owl

i think that its just names. like, they’re just called that cause thats the way it is. just focus on the difference in sounds rather than the names. im not totally sure about the names, but my second bit is true.