Why is this a Cmaj chord?

And couldn't it be a Gmaj instead?

Since noone has answered for a long time I'm going to play the expert.

This doesn't look like any chord I know. Bear in mind I have mostly studied major and minor chords, but the closest I could get to this chord played with the left hand was A 7sus4 (A - D - E - G, played from left to right of course.)

The problem is the note sequence on the picture (don't know if I should call it a chord as I don't know if it is one) starts on A and the inversions did not render the right results (E - G - A - D) either.

Thanks for the reply, i already got it answered.

Here are some replies i was given:

"Many combinations of notes can usually be named in several ways. The most meaningful name depends on the musical context that the chord is used in. As already mentioned, Am7 and C6 contain the same notes, A C E & G but the name you see will depend on how it's arranged to fit in with the key and other chords.

C major 7 contains the notes C E G & B. The notes C E G B & D make C major 9.

Context, permitting, if the C is omitted the chord can still function pretty much the same so it will often still be labelled C maj9 and called C major 9th or even a rootless C major 9th.

I don't know what that pic is explaining without a wider context. It's calling the chord C maj7 yet it contains the 9th D and the 6th, A. It doesn't contain the root C but as I said, there are many contexts where that's acceptable. It also doesn't contain B which is the major 7th - the note that puts the "major" in the chord name. "

by Fretsource

"The notes you gave here do not spell a traditional tertian chord so it's even harder to figure out.

E-G--D-[f#]-A would be Em11 or Em7add4 in Jazz.

But it could be other chords too. For example, it *might* be a C6/9 chord (C-E-G-A-D) if the C note were implied somewhere else. But without context, we can't be as sure as if it was simply E-G-B-D, which is solid enough to say it *is* Em7. "
by stevel

and

"He's using the triangle symbol to mean any major type chord, not just maj7. This particular one is a rootless C6/9 chord "