_:b670469247 . _:b670469247 . _:b670469247 "A solid or liquid particle, usually 0.2 micrometers in diameter, on which water vapour condenses, seeding cloud formation." . _:b670469247 "https://en.wikipedia.org/wiki/Cloud_condensation_nuclei" . _:b670469247 . _:b670469247 .