Wet is the highest degree of wetness. Moist, damp and humid are not as wet. When something is soaked in and is dripping of liquid, we call it wet. A swab well soaked with water is wet. Moist and damp have more or less the same degree of wetness, but moist is used mainly in places where the wetness is desirable, i.e. it is a positive word. Damp on the other hand is used when wetness is undesired, i.e it is a negative word. For example, if you play football (English - football/American - soccer) you will understand that a moist field is good, but a damp field is not. Cake and bread must be moist, but not damp. Clothes that aren't dry enough to be worn are damp, not moist. The mud by the river is damp. Humidity is connected with atmosphere/air. Air has moisture in it and it causes humidity, too much of which makes one feel damp.

One thing to add here, humid/humidity comes from the word humidite in old French. English has words coming from the old English Germanic language and old French. Since the elite spoke French in the middle ages, the word humid means almost the same as damp, but sounds a little bit more sophisticated. Compare freedom to liberty for example, same thing. Since English has two sources for its vocabulary there are a whole lot of, too many maybe, synonyms in the language.

Thank you very much, Su.Ki. :) I appreciate your concern. I've just remembered why I asked this question. I read the following sentences and couldn't get the difference between humid and damp "It can get hot in the summer for two or three months, and in the cities it is often humid. In the winter, it can be dry, sunny and freezing, or grey and damp." So you helped a lot.

Hi Dmitry I know that this is a resolved question, but I saw this and thought that there were a few more points worth adding: Wet is wet - I think that's clear. Damp versus moist: Tirtho is absolutely right about the distinction between desirable and undesirable. 'Moist' is positive eg you should make sure the soil is moist when you plant things in it, and a good cake should be moist. 'Damp' is always negative - nobody wants to wear damp clothes or live in a damp house. Humid versus damp: Again, as Tirtho correctly said, humid refers to atmosphere. When you are talking about weather/climate, the key distinction between humid and damp is to do with temperature. Humid refers to hot places with a lot of moisture in the air, damp to cool/cold places. The Amazon rainforest is humid. England is damp! I hope that makes the situation clearer still! Su. Ki. (with the impolite-sounding name)

Wet= liquid can be touched. moist= liquid can not be touched, but felt. damp= you can realize the effect of liquid. humid=...