Greek here, but in this case of Bloc if you intent to return a collection it will be better to use "contents" , other than that Stuart explanation is perfect. Even for a book we say "table of contents". "Content" is used to refer to a single item or the uniform structure or a collection of items as a whole than individual parts. So it depends 100% from the context and your intention of explanation.

On Sun, Mar 6, 2016 at 1:05 PM Ben Coman <btc@openinworld.com> wrote:

On Sun, Mar 6, 2016 at 5:20 PM, stepharo <stepharo@free.fr> wrote:
> Hi native english speaker
>
> what is the best content or contents?

Actually I couldn't say off hand.�� It depends on the context and I
can't think of a specific rule.�� I can only present a few examples.

The contents of the box.
The content of the book - but the book has a Table Of Contents.

Probably just best to refer to the experts: "grammar content versus contents"

http://dictionary.cambridge.org/grammar/british-grammar/content-or-contents

http://english.stackexchange.com/questions/13556/content-or-contents

http://blogg.lnu.se/english-language-blog/blog/maria/content-and-contents/

cheers -ben