Learn French: C'était un pari vraiment risqué.

Un pari (a bet) is the noun form of the verb parier (to bet). Transforming the action of betting into a noun allows you to summarize a whole situation in a single, neat concept. This makes your French sound much more concise and native-like.

How would we express this same idea without using the nominalized word pari?

If you wanted to use a verb instead of the noun phrase, you would have to construct a longer clause. For example, you might say Parier là-dessus était vraiment risqué (Betting on that was really risky) or Ce qu'il a parié était vraiment risqué (What he bet was really risky). Notice how nominalization makes the original sentence much cleaner!

Why does the phrase vraiment risqué go after the noun, rather than before it?

Risqué is an adjective formed from a past participle (from the verb risquer, to risk). In French, adjectives made from past participles almost always follow the noun. The adverb vraiment (really) must stay directly attached to the adjective it modifies, so the entire cluster vraiment risqué comes right after un pari.

Why is this sentence in the imperfect tense (c'était) rather than the passé composé?

C'était is used here as a descriptive refresher: you use the imperfect to describe a past state, condition, or opinion. You are explaining the ongoing nature or quality of the bet at that time, rather than reporting a specific, completed action on a timeline.