Parsing is the process of creating a parse tree for a textual unit. This unit may be for a line of code or a sentence. It is easy to do for computer languages, since they were designed to make the task easy. However, this has made it harder to write code. Natural language parsing is considerably more difficult. This is due to the ambiguity found in natural languages. This ambiguity makes a language difficult to learn but offers great flexibility and expressive power. Here, we are not interested in parsing computer languages, but rather natural languages.

A parse tree is a hierarchical data structure that represents the syntactic structure of a sentence. Often, this is presented as a tree graph with a root as we will illustrate shortly. We will use the parse tree to help identify relationships between entities in the tree.

Parsing is used for many tasks, including: