Final answer:
Condensation nuclei are particles of atmospheric dust around which cloud droplets form.
Step-by-step explanation:
Condensation nuclei are particles of atmospheric dust around which cloud droplets form. When water vapor in the air is cooled enough, it condenses into tiny droplets of liquid water. These droplets can aggregate and form colloid-sized particles, which can then grow into larger water drops or crystals that fall as precipitation, such as rain, snow, sleet, or hail.