what is the difference between relative humidity and humidity?

Question

most people say its the same thing but its not my science teacher told us it isn't the same thing but i forgot what the difference is

Answer 1

Humidity simply indicates the presence of water vapour in the air.It does not indicate how much water vapour is there.But relative humidity indicates how much water vapour is there in the air in percentage(for a particular temperature).
So,if water vapour is present in the air,then that air is called humid air,otherwise it is called dry air.So, the presence of water vapour in air attributs to it the property known as humidity.In other words humidity is a property of air.
Given quantity of air ,at a certain temperature,there is a definite maximum amount of water vapour which the air can hold.Thus if it holds the maximum amount, the relative humidity will be 100 percent.If it holds less than the maximum amount of vapour, the value of relative humidity will also be less proportionally.
So relative humidity is defined as the ratio of the amount of water vapour actually present in the air to the maximum amount of water vapour the air can hold at that temperature.R.H. is also known as the degree of saturation as the air gets saturated if it holds the maximum amount of water vapour.

Answer 2

Absolute humidity is the concentration of water vapor in air. Relative humidity is the concentration of water vapor in air relative to the saturation point (the most that air can hold at that temperature).

Answer 3

try this site

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