Dry Air

[Hileg]

Why is is on a phycrometric chart that the words "dry air" are used when the air could contain moisture or humidity?
Does this mean that anything not at saturation is dry regardless of moisture content.
Thanks

 

[imok2]

Dry air exists when all of the contaminants and water vapor have been removed from atmospheric air. By volume, dry air contains about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases. Dry air is used as the reference in psychrometrics.