This is the 1829th most frequent Russian word.
начались
"Начались" means "began" or "started" (plural form).
The word 'начались' is the past tense form of 'начаться,' used here to indicate that the action of classes starting has occurred.
Начались занятия в школе.
The school classes have started.
'Начались' here is used to describe the start of a weather-related event, emphasizing the action initiation.
Вдруг начались сильные дожди.
Suddenly, heavy rains began.
In this sentence, 'начались' marks the beginning of a significant event, specifically negotiations.