You already know the site, it has to be built in to every `/questions` query.  But, if you are querying separate sites with concurrent AJAX queries, merely encapsulate the site name in your AJAX callback.  [See this Stack Overflow question for an example of doing that in javascript.][1]

Alternatively, you can parse [the `link` property of the question response][2] to determine the site.

EG: The question response returns a `link` for each question like this:

    "link": "http://gaming.stackexchange.com/questions/176660/how-to-configure-applied-en"

So, just extract the domain:

<!-- language: lang-js -->

    var qLink   = "http://gaming.stackexchange.com/questions/176660/how-to-configure-applied-energistics-to-increase-item-count-to-an-exact-value-wh";
    var qDomain = qLink.match (/^https?:\/\/([^\/]+)/i)[1];
    // Yields: "gaming.stackexchange.com"

[You can then use the domain for the `site` for subsequent calls][3]:

> **Per-Site Methods**  
> Each of these methods operates on a single site at a time, identified by the `site` parameter. **This parameter can be the full domain name** (ie. "stackoverflow.com"), or a short form identified by `api_site_parameter` on the site object.

For example, these calls all yield the same results:

 - [api.stackexchange.com/2.2/questions?site=gaming](https://api.stackexchange.com/2.2/questions?site=gaming&pagesize=1)
 - [api.stackexchange.com/2.2/questions?site=gaming.stackexchange](https://api.stackexchange.com/2.2/questions?site=gaming.stackexchange&pagesize=1)
 - [api.stackexchange.com/2.2/questions?site=gaming.stackexchange.com](https://api.stackexchange.com/2.2/questions?site=gaming.stackexchange.com&pagesize=1)
 - [api.stackexchange.com/2.2/questions?site=arqade.com](https://api.stackexchange.com/2.2/questions?site=arqade.com&pagesize=1)
 - [api.stackexchange.com/2.2/questions?site=thearqade.com](https://api.stackexchange.com/2.2/questions?site=thearqade.com&pagesize=1)

(The last 2 domains are aliases for the Gaming site.)


----------
If you really want the English name, EG "Arqade", then **look up the domain**, as determined above, **in a table that your app cached** after calling `/sites` *once* per app session or once per day.

  [1]: http://stackoverflow.com/q/1194104/331508
  [2]: https://api.stackexchange.com/docs/types/question
  [3]: https://api.stackexchange.com/docs#tabs