Sould "soudain" not be "soudainement"?

Question

In this lesson, one of the examples is:On regardait les lucioles, et soudain elles ont toutes disparu.Why is it soudain and not soudainement?

Maarten Kamp · Answer

Danielle,

both ' soudain ' and ' soudainement ' can be used as adverbs.

When used away from the verb like this, it is quite colloquial to use ' soudain ' rather than ' soudainement " - ' tout à coup ' would be an alternative expression here.

' Soudainement ' is however typically used when following a verb directly.

"Soudain ' is also an adjective, of course.

See previous response from Cécile to a question on the same phrase :

https://progress.lawlessfrench.com/questions/view/soudain-vs-soudainement

https://www.wordreference.com/fren/soudain

https://www.wordreference.com/fren/soudainement