Well, first of all, I think you mean "humility". Humidity is a word that refers to how much water vapor is in the atmosphere. I'll just assume you mean "humility" :) The word "modest" generally means to have a medium amount of something. Not too much, not too little. The word "modesty" means to act in a modest way. Without any other context, it usually refers to how important a person acts. A person who is acting with modesty is acting as if they are not important. The word "humility" comes from "humble". When a person is humble, they think they are not important. Modesty is how a person acts. Humility is what a person thinks of themselves. For example, imagine someone gave you a great compliment. Modesty would be to act politely and not accept the compliment, even if you agree with the compliment. Humility would be if you really believe the compliment is not true.