I have just installed a new Wiki plugin for WordPress in which you can create multiple wikis as part of your WordPress blog. This is by far the easiest wiki plugin I have tried to use with WordPress. The plugin is not free, but I highly recommend this website here: https://premium.wpmudev.org/project/wordpress-wiki . Get the 1 year subscription. These guys are really great and the plugins are always updated to work with the latest version of WordPress.
I see a real benefit for this plugin when used inside our student publishing site called Engage. I know many teachers liked the idea of using WikiSpaces because it was a very simple way to maintain a website and work with students. Now they will have all the benefits of blogs plus the added ease and usefulness of a wiki.
Here is an example Link to my wiki: