Breakdown of Oli niin hirveä sumu, että en nähnyt mitään.
olla
to be
ei
no / not (en, et, ei, emme, ette, eivät)
nähdä
to see
niin
so
Questions & Answers about Oli niin hirveä sumu, että en nähnyt mitään.
The translation says "such a terrible fog", but doesn't niin usually mean "so"?
Yes! In English we often say "such a", but Finnish literally says "so terrible fog" (niin hirveä sumu). When using the niin ... että (so ... that) consequence structure with an adjective and a noun, niin acts as an adverb directly modifying the adjective.
Why does the sentence just start with oli? Shouldn't there be a word for "there"?
Finnish doesn't use dummy subjects like "there" or "it". To say "there was", you simply start an existential sentence with the verb olla in the third-person singular, which in the past tense is oli.
How is nähnyt formed from the verb nähdä (to see)?
To make the negative past tense, you combine the conjugated negative verb (en) with the active past participle. For nähdä (a type 2 verb), you remove the -dä infinitive marker and add -nyt, giving you nähnyt.