I know that the singular of *data* is *datum.* I know that *data* is a plural. 

However, common usage of the word "data" suggests it is used as a "collection of data".

> 
> Here is [the collection of] data.
> 
> 
> 

In which case, is the word *data* now a singular again, or still the plural? If so, what is the correct use of the word *data* and *datum* now?