Natural Language Processing (NLP) refers to AI method of communicating with intelligent systems using a natural language such as English.
Processing of Natural Language is required when we want an intelligent system similar to robot to perform as per your instructions, when you want to hear decision from a dialogue based clinical expert system, etc.
The field of NLP involves making computers to carry out useful tasks with the natural languages humans use. The input and output of an NLP system can be −
• Speech
• Written Text
Components of NLP
There are two primary components of NLP which are-
1. Natural Language Understanding (NLU)
Understanding involves the following tasks −
• Mapping the given input in natural language into useful representations.
• Analyzing different aspects of the language.
2. Natural Language Generation (NLG)
It is the process of producing meaningful phrases and sentences in the form of natural language from some internal representation.

It involves −
• Text planning − It includes retrieving the relevant content from knowledge base.
• Sentence planning − It includes choosing required words, forming meaningful phrases, setting tone of the sentence.
• Text Realization − It is mapping sentence plan into sentence structure.
Generally the NLU is harder than NLG.
Problems in NLU: NL has an extremely rich form and structure.
It is very ambiguous. There can be different levels of ambiguity −
• Lexical ambiguity − It is at very primitive level such as word-level.
• For example, treating the word “board” as noun or verb?
• Syntax Level ambiguity − A sentence can be parsed in different ways.
• For example, “He lifted the beetle with red cap.” − Did he use cap to lift the beetle or he lifted a beetle that had red cap?
• Referential ambiguity − Referring to something using pronouns. For example, Rima went to Gauri. She said, “I am tired.” − Exactly who is tired?
• One input can mean different meanings.
• Many inputs can mean the same thing.
NLP Terminology
• Phonology − It is study of organizing sound systematically.
• Morphology − It is a study of construction of words from primitive meaningful units.
• Morpheme − It is primitive unit of meaning in a language.
• Syntax − It refers to arranging words to make a sentence. It also involves determining the structural role of words in the sentence and in phrases.
• Semantics − It is concerned with the meaning of words and how to combine words into meaningful phrases and sentences.
• Pragmatics − It deals with using and understanding sentences in different situations and how the interpretation of the sentence is affected.
• Discourse − It deals with how the immediately preceding sentence can affect the interpretation of the next sentence.
• World Knowledge − It includes the general knowledge about the world.

Author: Vivek Sharma