This is the 650th most frequent Hungarian word.
hirtelen
Suddenly.
The word 'hirtelen' is used as an adverb to describe the unexpected and sudden stopping of the car.
Hirtelen leállt az autó az úton.
The car suddenly stopped on the road.
Here, 'hirtelen' functions as an adjective describing the sudden nature of the movement.
A hirtelen mozdulattal leverte a poharat az asztalról.
With a sudden movement, they knocked the glass off the table.
In this sentence, 'hirtelen' is used adverbially to emphasize the unexpected occurrence of the thought.