Fog
Fog, or mist, was a concentrated suspension of water vapor that formed when water condensed into tiny liquid water droplets in the air.

Fog was present around the building of the Vulcan monastery at P'Jem. ()

Cyrus Ramsey's molecules were said to re-materialize on foggy nights. ()

Fog is highly unlikely on a planet with no cloud formations, bodies of water, or changes in surface temperature. Despite lacking these features, Korob created fog on the planet Pyris VII by telepathically drawing the image of fog from the  landing party in 2267. ()

That same year, when the Enterprise visited Argelius II, the fog was very heavy on the planet's surface. ()

Several years later in 2270, the Enterprise computer created fog on the bridge of the starship after a strange space cloud caused it to gain artificial intelligence and start playing practical jokes on the crew. ()

When the away team from the  beamed down to the surface of the planet Minos, they beamed into a foggy jungle-like environment. ()

Due to the cold temperatures, the interior of the space module was full of frozen fog. ()

The streets of London were notoriously foggy. Sherlock Holmes Program 3A faithfully depicted this. ()

In 2370, fog suddenly rolled in on the bridge of the Enterprise-D when the ship's environmental controls malfunctioned due to feedback from one of Caldos colony's weather substations. Data estimated the fog's temperature to be 1 °Celsius. ()

Michael Eddington described the planet Athos IV, located in the Badlands, as "a grim little fogbound piece of rock in the middle of nowhere." The heavy fog on the planet made it difficult for Eddington and Captain Benjamin Sisko to identify Jem'Hadar soldiers guarding the Maquis compound. ()

Laas, a Changeling, turned himself into fog on the Promenade of Deep Space 9 in 2375, much to the displeasure of many around him. () 

In 2376, Tom Paris created a holodeck program of a 19th century Irish town called Fair Haven, complete with fog. Harry Kim thought the program needed more fog to make the program authentic, but Tom disagreed as he found fog depressing. Tuvok had no opinion on the matter. ()

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de:Nebel (Atmosphäre)
Meteorology