What is the difference between relative humidity and regular humidity?
It can be assumed that any weather use of the term humidity is actually about relative humidity. Relative humidity is the water vapor content of the air relative to its content at saturation. The moisture content, or saturation point, of air depends on air pressure and especially temperature, so when scientists refer to relative humidity, they have attempted to measure both these factors to tell us how wet the air is. We’re still a bit confused about this, but if the relative humidity is 100 percent, that’s pretty wet and heavy air, which is why we’re so uncomfortable trying to breathe it.