DEW-during winter nights,the atmospheric temp goes down.the surfaces of window panes,flower,grass,etc,become still colder. the air near them becomes saturated with vapour & condensation begins.the water droplets condensed on such surfaces are known as dew.
IF THE TEMP FALLS FURTHER,THE WHOLE ATMOSPHERE IN THAT REGION CONTAINS A LARGE AMOUNT OF VAPOUR
so the water molecules present in vapour condense on the dust particles in air and form small droplets of water. these droplets keep floating in the air & form a thick mist which restricts visibility. this thick mist is called fog.