I've been teaching myself to play guitar without any formal instruction. Occasionally, in a tab I'll find a new chord labeled somewhere along the lines of "Cadd9" or "Dsus4". What do these mean?
I've tried searching online, but all I've found are websites showing how to play these chords.
add= addition onto chord
Cadd9 = add ninth from root note onto C triad = CEGD
sus= suspended chord
Dsus4= D triad take away major third and add a perfect 4th i.e. DGA
The answer above explains how those two specific chords are built and spelled. These are extended chords in the first instance and suspended chords in the second instance. If you are interested in studying how triads, extended chords and altered chords are built and spelled, I recommend books about harmony and music theory. There are books that are above many folks understanding, but there are also books written in easily understood language and form. They can give you answers to many of your questions and a new understanding of the art form. Personally, I love studying the stuff.
You may find that the explanations above, as relevant as they may be, a little unsatisfying. You are obviously enthusiastic but you are leaving great gaps in your learning if you do not start learning music theory from scratch.
If you do not want a formal education, use the internet. You can choose the websites you want and can move at your own pace BUT. Be very careful which websites you get into, some on you tube are made from people who have had a few music lessons and suddenly set themselves up as teachers. Just check that the websites are from qualified teachers or organisations and your enjoyment will increase. Good luck
