Questions & Answers about Vem glider fortast i det långa spåret?
Why is it fortast here, and what is the base form of this adverb?
The base form is fort (fast or quickly). Because the sentence asks who glides fastest, we use the superlative form fortast. To make the comparative and superlative forms of regular adverbs, you usually add -are and -ast to the base form. This gives us: fort (fast), fortare (faster), and fortast (fastest).
Could I use snabbast instead of fortast here?
Yes, you could also say Vem glider snabbast. The word snabb is an adjective, but its neuter form snabbt is used as an adverb, and its superlative is snabbast. Both work, but fort is strictly an adverb of speed and is very natural to use here because it describes the action of the verb glider (glides).
Why do we need both det and the -et ending on spåret?
This is a great example of the Swedish double definite rule. When a definite noun like spåret (the track) is described by an adjective like långa (long), you must also put a freestanding definite article in front of the adjective. Since spår is an ett-word, we use det, giving us det långa spåret (literally: the long the track).
Why does the adjective end in an ?