<s>[INST] Define a formal language and an informal language. Formal languages have the following properties: property (1) the words used to communicate are precise and well-defined, and property (2) there is a precise set of rules that defines how these words are to be used. In other words, a formal language has a well-defined syntax. Provide an example of a formal language and explain how it embodies the above two properties. Provide an example of an informal language which lacks both of these properties.[/INST]