How to use wikipedia api if it exists?

See http://www.mediawiki.org/wiki/API

Specifically, for the English Wikipedia, API is located at http://en.wikipedia.org/w/api.php

You really really need to spend some time reading the documentation, as this took me a moment to look and click on the link to fix it. :/ but out of sympathy i'll provide you a link that maybe you can learn to use.

http://en.wikipedia.org/w/api.php?action=query&prop=revisions&titles=New_York_Yankees&rvprop=timestamp|user|comment|content

That's the variabled you will be looking to get. Your best bet is to know the page you will be after and replace the Wikipedia link part into the title i.e.:

http://en.wikipedia.org/wiki/New_York_Yankees [Take the part after the wiki/]

-->

http://en.wikipedia.org/w/api.php?action=query&prop=revisions&titles=New_York_Yankees&rvprop=timestamp|user|comment|content

[Place it in the title variable of the GET request.

The URL above can do with tweaking to get the different sections you do or do not want. So read the documentation :)

Have a look at the ApiSandbox at https://en.wikipedia.org/wiki/Special:ApiSandbox That is a web frontend to easily query the API. A few clicks will craft you the URL and show you the API result.

That is an extension for MediaWiki, enabled on all Wikipedia languages. https://www.mediawiki.org/wiki/Extension:ApiSandbox

The answers here helped me arrive at a solution, but I discovered more info in the process which may be of advantage to others who find this question. I figure most people simply want to use the API to quickly get content off the page. Here is how I'm doing that:

Using Revisions:

//working url:
http://en.wikipedia.org/w/api.php?action=query&prop=revisions&titles=Threadless&rvprop=content&format=json&rvsection=0&rvparse=1

//Explanation
//Base Url:
http://en.wikipedia.org/w/api.php?action=query

//tell it to get revisions:
&prop=revisions

//define page titles separated by pipes. In the example i used t-shirt company threadless
&titles=whatever|the|title|is

//specify that we want the page content
&rvprop=content

//I want my data in JSON, default is XML
&format=json

//lets you choose which section you want. 0 is the first one.
&rvsection=0

//tell wikipedia to parse it into html for you
&rvparse=1

Using Extracts (better/easier for what i'm doing)

//working url:
http://en.wikipedia.org/w/api.php?action=query&prop=extracts&titles=Threadless&format=json&exintro=1

//only explaining new parameters
//instead of revisions, we'll set prop=extracts
&prop=extracts

//if we just want the intro, we can use exintro. Otherwise it shows all sections
&exintro=1

All the info requires reading through the API documentation as was mentioned, but I hope these examples will help the majority of the people who come here for a quick fix.