Any combination of at least seven glyphs required to generate a destination through which one may travel through the Stargate
to another world. The first six glyphs pinpoint a three-dimensional location in space. The seventh represents a point of origin. An eighth, and extremely rare, glyph denotes a different galaxy, akin to dialing a different area code.
Addresses are not random. One could stand at a D.H.D. for considerable periods of time, entering thousands of various combinations and never lock into a destination. It is believed there are a probable 63 billion combinations (ten Stargates for every person on Earth). This means an equal number of Stargates could potentially exist in the galaxy.
There are nine chevrons for the Stargate to engage glyphs. The purpose of the ninth chevron is presently unknown.
"Stargate" the Movie - Daniel Jackson locates the Earth's point of origin on the Stargate, allowing the personnel to complete the address and lock on to Abydos.
Avenger 2.0 - Felger's lab assistant, Chloe, tells Carter and Jay of the potential 63 billion Stargate address combinations.
Air, Part 1 - Nicholas Rush and the Icarus Base dial the only known 9-symbol Stargate address, connecting them to the Ancient vessel Destiny in a distant galaxy.