Actually I am pretty sure we shouldn't have heard the f because it's the singular form..
2 years later edit: Seems like the old me was pretty sure without any valid reasons.. I must admit I am confused about the correct way and I would love for someone who knows better to clarify this matter if possible.
This sentence always makes me picture a hollowed-out cake with a whole egg just sitting inside it. I don't think I would ever say it that way in english. I would just say "there's egg in the cake", and specify a number or amount if asked. And the amount is 3. If you only use 1, you're making brownies, not cake :|
It's optional after verbs, except when followed by a pronoun: http://french.about.com/library/pronunciation/bl-liaisons-o.htm
Would this mean the cake is made with egg?
The English "the cake contains AN egg" suggests the egg is intact - something like there being a hard boiled egg in the middle - whereas, the "cake contains egg" would suggest the far more plausible situation that the cake is made with egg.
You seem to be saying that there are contexts where this is a perfectly way of referring the egg used in a cakes batter - I'm not sure I agree.
Personally - and dialects are different of course - I would never say "the cake contains one egg" when comparing recipes I might say "the recipe requires one egg", or I might say informally "the cake has one egg". The latter is a very imprecise way of speaking, and could be paraphrased in any number of ways. Contrast this with using "contains" where the specificity of the word implies that its use was very deliberate and care is being taken with its application.
As such, it becomes a problem that once the egg is mixed into a batter it ceases to be "one egg" (count noun) and becomes "some egg" (mass noun). An egg that has been used to make a cake is not a whole egg, and referring to it as "an egg" would be wrong.
So, to me "the cake contains an egg" suggests that it is still whole. And looking at the other comments, I don't think I'm the only one. My question is whether the French phrase has the same implications.
Would this sentence be actually used in french .In english this sounds oddIt would more likely be the " cake contains egg", or "egg is an ingredien"t. My image of this sentence is an egg, whole in a shell in the middle of a cake a little like ice cream in the middle of baked alaska. I think the translation for a realistic sentence should not have the indefinite article.
Inf. contenir. It is conjugated irregularly like tenir, see Duo (hover over contient) or