This is the 676th most frequent Slovak word.
reakcii
"Reakcii" in English means "reaction" (dative or locative singular form in Slovak).
In this sentence, 'reakcii' is a noun in the dative singular form, used to specify that the answer was a response to a preceding question.
Mária odpovedala v reakcii na otázku učiteľa.
Maria replied in reaction to the teacher's question.
Here, 'reakcii' indicates a causative relationship between the criticism and the improvement in performance.
V reakcii na kritiku zlepšil svoj výkon.
In reaction to the criticism, he improved his performance.
In this context, 'reakcii' is again a noun referring to the act or behavior exhibited in response to an event.