Question: I am learning to play guitar by myself, and it is hard to understand some theory about how guitar chords are built. For example let's look at a G chord. I have found two of the most simple definitions:

[![G chord](https://i.stack.imgur.com/zP4WA.png)](https://i.stack.imgur.com/zP4WA.png)

If we write down corresponding notes for both of them we will get:

* **G B D G** for the former
* **G B G** for the latter

But as I understand major chords are built from 1st, 3rd and 5th notes of the major scale, which is:

**G A B C D E F# C**

Therefore it should be **G B D**. Where am I wrong?

The same question is about E chord.

[![E chord](https://i.stack.imgur.com/FyV4T.gif)](https://i.stack.imgur.com/FyV4T.gif)

Notes are: **E B G** whereas according to the scale **E F# G# A B C# D# E** it should be **E G# B**.

And one more question. How is it possible for chord to have more than 3 notes, like the G chord on the 3rd fret, if the chord is a triad?

Answer: 
> 
> How is it possible for chord to have more than 3 notes, like for G chord on 3rd fret, if chord is a triad?
> 
> 
> 

A chord with three scale degrees doesn't have to only have three notes - it can contain repetitions of those notes in different octaves.

> 
> [![G chord](https://i.stack.imgur.com/zP4WA.png)](https://i.stack.imgur.com/zP4WA.png)
> 
> 
> If we write down corresponding notes for both of them we will get:
> 
> 
> * **G B D G** for the former
> * **G B G** for the latter
> 
> 
> 

In both of these diagrams, you can play *all* the strings - not just the ones you put your fingers on! So actually you have 

* **G B D G D G** for the former
* **G B D G B G** for the latter

So, you see that these chords *are* made up of the notes G, B, D - it's just that some of them are repeated.

So, how do you know when you can play the open strings (the ones without your finger on?

[![enter image description here](https://i.stack.imgur.com/8yTgF.png)](https://i.stack.imgur.com/8yTgF.png)

Take a look at this picture. The G string (that you *should* play) has a **O** symbol, which means you should play the string. But the E strings have an **X** symbol, meaning that you shouldn't.
It's a strange concept for beginners to grasp, but yes, you're correct, a triad chord has three notes. However (there's usually one of those), there's nothing to say *how many* of each there are. One of each is fine - without all three, it's not a triad - but we then get into *voicing*, which makes each chord sound subtly different. 

Guitar is really a special case, because of the 6 strings. What I do with students at some point is to present a triad. Let's say C major, CEG. Take each string in turn, and find a C, E or G playable on it. Obviously when the notes have been found, they must be playable simultaneously, otherwise it can't be a 6 string guitar chord.

6th string could be E or G. 5th is C. 4th makes E. 3rd, open is G. 2nd finds another C, and top can be E or G. So now we have 4 different versions of Cmaj. All with *some* Cs, *some* Es and *some* Gs. All can be classed as correct, but some sound better in certain songs than others.