fog vs fug

fog and fug both are nouns.

Word	Noun	Adjective	Verb	Adverb
fog	Yes	No	Yes	No
fug	Yes	No	No	No

As nouns, fug is a hyponym of fog; that is, fug is a word with a more specific, narrower meaning than fog:

fog: an atmosphere in which visibility is reduced because of a cloud of some substance
fug: (British informal) an airless smoky smelly atmosphere

fog (noun)	fug (noun)
confusion characterized by lack of clarity	(British informal) an airless smoky smelly atmosphere
droplets of water vapor suspended in the air near the ground
an atmosphere in which visibility is reduced because of a cloud of some substance

fog (verb)	fug (verb)
make less visible or unclear