Do you think it's a good practice to differentiate abstract from non-abstract classes by giving their name a prefix or a suffix? What are the most common practices when it comes to that?

Here are a few "formats" I've been thinking about: 

* Foo\_Base
* Foo\_Abstract
* Abstract\_Foo
* Base\_Foo

The use of underscores and letter case is irrelevant.

Edit: It seems like the Zend Framework uses a "Abstract" suffix ([source](http://framework.zend.com/manual/en/coding-standard.naming-conventions.html)).