Elle a dû oublier de t'appeler. Why is there a "de" between oublier and t'appeler?

Question

Elle a dû oublier de t'appeler.Hello why is there a "de" between oublier and t'appeler?I often see a "de" in sentences whose placement I can't really understand. I would like to know if there is a rule for this.

Accepted Answer

Hi Sam,
There are lots of verbs in French which (when they are followed by another verb) have to have the preposition 'de' or  'à' before the second verb in the infinitive.
I am working on some study lists for such verbs which you can look out for in the future.
In the meantime, here are a few -
Oublier de [faire] = To forget [to do something]
Accepter de [faire] = To accept [to do something] 
Choisir de [faire] = To choose [to do something]
Arrêter de [faire] = To stop [doing something]
etc.
Hope this helps!

Answer

And just to add a bit of rascally (but correct) excess to the great answer by Cecile, I will add, please remember that this odd looking *de* occurrence does not only appear between two verbs.

Or as Cecile may say in french at the end of her list..

"Vous devez vous souvenir de ca"/ You have to remember that!... which to me is one of the funniest occurrences of 'de' and hard to get your mind around but cool once learnt.

Good luck from one learner to another!

Answer

Very interesting comment, Jameson, we natives don't always see the problems you encounter and this is one which would have eluded me...