Syntax Analysis

  First we should define Syntax Analysis:  parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar.

The traditional grammatical exercise of parsing involves breaking down a text into its component parts of speech with an explanation of the form, function, and syntactic relationship of each part.

 We should  differentiate  between category and function

Category differs from function because category denotes what a word is while function denotes what a word does. 

What kind of [sentence] constituent is this? — This question denotes category.

What role does this [sentence] constituent perform? — This question denotes function. 

Category denotes the kind a word is while function denotes the role a word performs in a sentence: "Cat" is a lexical, open class kind of sentence constituent and is a noun that performs the role of Subject in a matrix (independent) clause noun phrase while, in contrast, "by" is a grammatical, closed class kind of sentence constituent and is a preposition that performs the role of head preposition signifying proximity in a prepositional phrase.

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