The categories of count and non-count nouns can be confusing, however, and we suggest further review, especially for writers for whom English is a second language. The second section we offer is called Count and Non-Count , a basic review of those concepts and their uses in sentences, with many examples. Third, we offer WORKING WITH NOUNS , a more extensive (and somewhat more advanced) review of the count and non-count distinction, along with exercises. Finally, just when you thought you couldn't stand such riches, we suggest you review the uses of Articles, Determiners, and Quantifiers with count and non-count nouns.
Suppose we were modeling the behavior of animals, by creating a class hierachy that started with a base class called Animal. Animals are capable of doing different things like flying, digging and walking, but there are some common operations as well like eating and sleeping. Some common operations are performed by all animals, but in a different way as well. When an operation is performed in a different way, it is a good candidate for an abstract method (forcing subclasses to provide a custom implementation). Let's look at a very primitive Animal base class, which defines an abstract method for making a sound (such as a dog barking, a cow mooing, or a pig oinking).