An interesting question, touching on a point of syntax I do not see in
my grammar references. Let us explore.
Intuitively, a native English speaker recognizes that the before
names is optional in each of these cases. (The last sentence is
different syntactically, and is not addressed in this answer.) Here are
some similar constructions where the is likewise optional:
- [The] leaders of democratic nations are usually persuasive public speakers.
- [The] shorelines of lakes are sometimes highly developed.
- [The] covers of graphic novels often feature a dramatic scene from the story.
In each of these cases, as well as the cases in the question, the is
only optional because the noun it modifies is also being modified by a
prepositional phrase — “of languages”, “of democratic nations”, “of
graphic novels”. Without such a prepositional phrase, we would be
referring to names, shorelines, etc. in general, and the use of the
would be incorrect (unless an earlier sentence had specified what names
or shorelines we are referring to). With such a phrase, the can be
used or omitted, and the sentence sounds correct either way. Why?
I think it is because the noun phrase in these cases is a sort of
hybrid. The noun can be viewed as a generic noun (names, leaders,
shorelines, covers in general), which cannot take the; but it can
also be viewed as one that, having been specified (names of languages,
shorelines of lakes), does take the. Consider these phrases:
- Covers of graphic novels
- The covers of graphic novels
The first usage seems more generic: covers of all graphic novels,
considered as a class. The second seems more specific: which covers?
As I said, a most interesting question, and one that I was unable to
find addressed in my reference materials. I did find some material
online addressing similar issues: