One of the most powerful features of Drupal is the taxonomy system.

The word taxonomy comes from the ancient Greek word meaning 'the practice and science of the classification of things.

Consider a real-world example where Drupal might be used to manage, search, and display your music collection. It would be very useful to be able to categorize tracks within, for example, genre, because that way you could easily filter the entire collection down to say "soul" or "disco". Moreover, if you categorize the music tempo to say "slow", "medium", and "upbeat", then preparing a playlist of slow soul tracks would be simple just as you probably routinely do when using a dedicated organizer such as iTunes.

Thus, Drupal's taxonomy system is simply a means of enabling you to classify your content in many different ways.

The core taxonomy system allows you to define one or more vocabularies, each of which is a list of terms. For example, you may want to define an Article category vocabulary and associate...