вдруг

вдруг

Suddenly.

Here, 'вдруг' is used to indicate an unexpected or sudden occurrence.

Я шёл по улице, вдруг пошёл дождь.

I was walking down the street, and suddenly it started to rain.

In this sentence, 'вдруг' emphasizes the abruptness of the change in behavior.

Вдруг они начали смеяться, хотя всё было серьёзно.

Suddenly, they started laughing, even though everything was serious.

This use of 'вдруг' conveys the surprise element in the situation becoming significant.

Мы не знали, что вдруг это станет важным.

We didn't know that, all of a sudden, this would become important.