TOUGH TO GRASP

i dont get chords and intervals names why is it that a Cdim7 has a major sixth instead of a flat 7 and why does a Cmaj9 have a a major 7th as well as a major ninth? going strictly on interval names a Cmaj9 should just contain C,E,G,D WHY IS IT SO COMPLEX ADDING NOTES IN WHEN THE NAME SUGGEST DIFFERENT ITS TOUGH TO GRASP.HELP ME UNDERSTAND IN SIMPLE TERMS ANY1.

Dim is easy.
It's a chord made up of minor thirds.
So
Root / minor third / flat fifth / double flat seventh.
A C Eb Gb (play these notes on a single string on your fretboard and you will see it's all the same distance)

9 is 7 + 2.
So a maj9 chord is maj 7 plus a 2.

It's really pretty simple. a 13 is 7 plus 6 an 11 chord is 7 plus 4.
The add9 was a name thought up by people who didn't know what they were doing, it should be called an add 2.

harmony is based of thirds. the chords come from scales. so you get the scale get the tonic of the scale get it's third. then get the third's third. and so on. now there is many exceptions and it only works with the diatonic scales.

for example, major 13 if you get all the notes working in thirds you will get 1 3 5 7 9 11 13. but major 13 doesn't have 11 because the 11 is very dissonant so is omitted that's also why you will almost never see a major 11.

also on a side note 9,11, and 13 are just a 2,4,and 6 an octave higher

They are not.
9 11 13 are 7 + 2 4 6.
Also EVERY add 2 add 4 add 6 is an octave higher since we don't invert add chords.
Which is why I said the add9 is a notation made by people who didn't know what they are doing.

Not really, music just evolves. There is no set rule... rather; they're guidelines. You get 9 chords in Jazz standards, so they've been around for a pretty long time.

Unfortunately, Casano, there are some things that we just need to accept. Like; "why is a tree a tree?"

Cmaj9 has a 7 because the 9 wasn't in brackets, so naturally, everything above will always have an added seventh, just like there's a fifth or a third UNLESS; If it was written like Cmaj(9) then it would only be an added 9.

Afro explained it in quite a unique way, which I thought was one of the best ways to explain it to those who haven't got a starting clue about it... unfortunately i can't remember which topic it was written on. So I suggest you PM him about it.

thats what i mean ra interval names are a misnomer because following what you said about going in thirds the 11 should be in a maj13 but its not so its a flawed system.

it's not flawed it is how it works there just exceptions you understand English you should know this. this language is messed up remember y before e except after c in grammar school. the 11 is a exception in major chords because of the dissonance due to the minor 2 interval with the 3.

There is an 11th in a major 13th chord, but it is often left out when played on guitar because a full 13th chord has 7 notes, and there are only 6 strings.

edit, I give up.
Last thing I'll say here is the guitar is not a piano, we live by different theory on chords.

Best of luck to anyone who will ever seriously attempt to master the guitar.