Tagging is the process of assigning a description to a token or a portion of text. This description is called a tag. POS tagging is the process of assigning a POS tag to a token. These tags are normally tags such as noun, verb, and adjective.

For example, consider the following sentence:

"The cow jumped over the moon."

For many of these initial examples, we will illustrate the result of a POS tagger using the OpenNLP tagger to be discussed in Using OpenNLP POS taggers, later in this chapter. If we use that tagger with the previous example, we will get the following results. Notice that the words are followed by a forward slash and then their POS tag. These tags will be explained shortly:

The/DT cow/NN jumped/VBD over/IN the/DT moon./NN

Words can potentially have more than one tag associated with them depending on their context. For example, the word "saw" could be a noun or a verb. When a word can be classified into different categories, information such as its position...