PS You ask: "in fact how many inversion G5 chord can make"... Well, it's not a Zen koan: there are 3 inversions... There are 4 for a G7 chord. You add an extra tone to the chord and thus have one extra inversion. There isn't anything to argue about, but if you have any questions about inversions or tensions I'd be happy to answer them (or consult my girlfriend, who has more rigorous jazz studies under her belt, and can play a mean jazz trumpet despite being a classical horn player... speaking of talented lamma residents!)

Weird -- didn't know that about guitar. I figured Funkyjazzy was using a strange name for a G triad (since the G7 has 4 notes, G9 has 5 notes, etc., I figured G5 just referred to the triad). Thanks for the info! There's my classical training rearing its ugly head -- haha, are we more or are we less sophisticated for not considering an open fifth a chord?

http://en.wikipedia.org/wiki/Power_chord