LibAnswers

It depends how you use Wikipedia. Don't cite it in your paper, but it can help you discover independent sources for the facts and ideas that are summarized in Wikipedia.

A word of warning: your instructors may have strong opinions about Wikipedia, so check with them first! Your grade may be at stake.

Citing Wikipedia as a source is usually a bad idea.

Why?

Academic writing emphasizes sources that are close to the events or phenomena being discussed. This means using primary sources, such as original scientific research, actual laws, eyewitness testimony, etc., or sophisticated secondary sources, written by experts who have reviewed the primary sources.  Encyclopedias, such as Wikipedia, only summarize the findings of secondary sources. They are not close to the things being studied. Because of this, it is best to start with encyclopedias for helpful overviews, but then to seek more original sources to base your paper on.

Furthermore, Wikipedia articles can be written or revised by anyone at any time. You can't know anything about the expertise, bias, or motivations of the many authors contributing to an article. Because of this, you can't evaluate its reliability. Finally, Wikipedia is at risk for the spread of biased information by anonymous authors. Academic writing is based on more foundational sources.

Wikipedia can help you find relevant external sources

One  important benefit of Wikipedia is that many articles cite the sources for their claims. These sources are separate from Wikipedia. Often you can link to these external sources and evaluate them yourself. If the source is good, then you can rely upon it for your paper. Don't cite Wikipedia, but let it point you to promising sources.

How to use Wikipedia's citations

• Citations are marked with superscript numbers. The citations come immediately after the borrowed material. You can "mouse over" the number for a quick citation, or you can click it to see the list of citations at the bottom. 
• Here is an statement from an (archived) Wikipedia article on dogs. 

Dogs generally show reduced fear and aggression compared with wolves.^[61][63]

To see the source of this statement, you would "mouse over" one of the superscripts: [61] or [63].

• The first note would give this article citation. The title link opens the full text.

Cagan, Alex; Blass, Torsten (2016). "Identification of genomic variants putatively targeted by selection during dog domestication". BMC Evolutionary Biology. 16: 10. doi:10.1186/s12862-015-0579-7. 

• The second note would give this book citation:

Coppinger R, Schneider R: Evolution of working dogs. The domestic dog: Its evolution, behaviour and interactions with people. Cambridge: Cambridge University press, 1995.

These are both good sources for your paper. You could borrow from them directly and cite them.

Many citations include links to full text, but many do not. If you want to find the source, contact a librarian on LibChat, or sometimes you can find an article by copying its citation into Google Scholar.