Is there an equivalent to wetness for air? I was wondering if there was something equivalent to the property of being wet with water, but with air instead. For example, if I drop water on my shirt, I'll notice by its appearance and feel that it is wet, so in a sense its properties were changed by being exposed to water.
So I'm wondering if similarly, by being exposed to ambient air, my shirt is somehow being changed, i.e. if it was in a vacuum would it feel or appear different than when it's exposed to air?
 A: Well - air does have "relative humidity" and this really affects the things that interact with it. For example - you will have a hard time cooling down by sweating when the relative humidity is very high, as the rate of evaporation that you can achieve (and therefore heat rejection) becomes quite low: this is why you end up "sweaty" on a hot muggy day.
Similarly, materials like nylon are very hygroscopic: when they are in humid air, they will absorb some of that moisture. This will affect their mechanical properties. An extreme example of this can be seen with sugar and salt - they will "melt" when exposed to humid air for a while.
If we are talking about "pure air", then we still see this effect. There are chemical reactions (mostly with the oxygen in the air) that can result in changes. For example, various metals will oxidize when left unprotected in the air: you could say they became "wet". Exposing them to a reducing environment (e.g. hot hydrogen gas) could "dry" them again, as the oxygen is reduced and the surface once again becomes metallic.
I hope that I didn't completely misunderstand your question...
