What are conditions called when droplets of water collect in air at the earth's surface?

Droplets of water collecting in the air at the earth's surface is specifically referred to as fog. Fog is a type of low-lying cloud that forms when the air is saturated with moisture, causing tiny water droplets to condense and become suspended in the air near the ground. This results in reduced visibility and the characteristic low, thick appearance of fog that can be observed during certain weather conditions, typically when warm, moist air comes into contact with cooler surfaces.

The other terms refer to different phenomena: humidity is a measure of the amount of moisture in the air but does not describe the physical collection of water droplets; rain refers to precipitation in the form of larger water droplets that fall to the ground from clouds; and clouds are visible masses of condensed water vapor floating in the atmosphere but are not restricted to the surface level. Therefore, fog is the most accurate term for the described condition.