Prevenire vs. evitare vs. impedire vs. scongiurare
The Italian verbs prevenire, evitare, impedire, and scongiurare can all be translated as to prevent in English, but they focus on different aspects of keeping something from happening. The difference lies in whether you are anticipating a problem, dodging an issue, physically blocking an action, or averting a major catastrophe.
Prevenire
The verb prevenire means to prevent by taking action in advance. It focuses heavily on anticipation and foresight, much like the English concept of preventative care or taking precautions before a problem even exists.
Dobbiamo prevenire la diffusione del virus.
(We must prevent the spread of the virus.)
Prevenire è meglio che curare.
(Prevention is better than cure.)
Un corretto stile di vita aiuta a prevenire molte malattie.
(A proper lifestyle helps prevent many diseases.)
Hanno installato telecamere di sicurezza per prevenire i furti.
(They installed security cameras to prevent thefts.)
Evitare
The verb evitare directly translates to to avoid or to bypass. While it can mean keeping something from happening, it focuses on sidestepping a negative outcome or keeping oneself away from a bad situation altogether.
Ho preso una strada secondaria per evitare il traffico.
(I took a back road to avoid the traffic.)
Voglio evitare di fare gli stessi errori del passato.
(I want to avoid making the same mistakes of the past.)
Hanno lavorato tutta la notte per evitare un ritardo nella consegna.
(They worked all night to avoid a delay in delivery.)
Il pilota ha fatto una manovra rapida per evitare l'ostacolo.
(The pilot made a quick maneuver to avoid the obstacle.)
Impedire
The verb impedire means to prevent by putting up a physical or abstract obstacle. It is often used when stopping someone from doing something, acting as a block, or rendering an action impossible.
La forte nevicata ci ha impedito di partire per la montagna.
(The heavy snowfall prevented us from leaving for the mountains.)
Nessuno ti impedirà di esprimere la tua opinione.
(No one will prevent you from expressing your opinion.)
Un muro molto alto impedisce l'accesso al cortile privato.
(A very tall wall prevents access to the private courtyard.)
Il tempestivo intervento della polizia ha impedito una rissa.
(The timely intervention of the police prevented a brawl.)
Scongiurare
The verb scongiurare means to avert, to ward off, or to prevent a major crisis or disaster. It is a dramatic word used when a highly negative worst-case scenario is successfully avoided.
L'accordo diplomatico dell'ultimo minuto ha scongiurato la guerra.
(The last-minute diplomatic agreement averted the war.)
I medici sono intervenuti subito e sono riusciti a scongiurare il peggio.
(The doctors intervened immediately and managed to avert the worst.)
Il governo ha varato misure urgenti per scongiurare la crisi economica.
(The government passed urgent measures to avert the economic crisis.)
La rapida evacuazione dell'edificio ha scongiurato una tragedia.
(The rapid evacuation of the building averted a tragedy.)
Summary
To summarize: use prevenire when acting in advance to stop a problem from forming, evitare when dodging or bypassing an unpleasant situation, impedire when actively blocking someone or making an action impossible, and scongiurare when warding off a major catastrophe.