reaction
The French word 'réaction' is used in the same way as the English word 'reaction'. It refers to a response to a particular situation or stimulus. For example, 'sa réaction à la nouvelle était très positive' means 'his reaction to the news was very positive'.
What is your reaction to this news?
In this sentence, 'Quelle est votre réaction à cette nouvelle?' is a question asking someone's response or feeling to a certain news. 'Quelle' means 'what', 'est' is 'is', 'votre' means 'your', 'réaction' is 'reaction', 'à' is 'to', and 'cette nouvelle' means 'this news'.
The chemical reaction produced water.
In the sentence 'La réaction chimique a produit de l'eau.', it expresses a scenario where a chemical reaction resulted in creating water. 'La' is 'the', 'réaction chimique' is 'chemical reaction', 'a produit' means 'produced', and 'de l'eau' is 'water'.
His quick reaction saved lives.
The third sentence, 'Sa réaction rapide a sauvé des vies.', speaks of a situation where someone's prompt response resulted in saving lives. 'Sa' is 'his', 'réaction rapide' means 'quick reaction', 'a sauvé' is 'saved', and 'des vies' means 'lives'.