Understanding Ambiguities in Natural Language Processing
While Natural language processing (NLP) tries to understand the language in which humans communicate it faces several challenges. Ambiguity of words/sentences/phrases is one among them. Let us discuss the various types of ambiguities that need to be addressed to have the right interpretation of language.
Types of Ambiguities
1. Lexical Ambiguity
Lexical means relating to words of a language. During Lexical analysis given paragraphs are broken down into words or tokens. Each token has got specific meaning. There can be instances where a single word can be interpreted in multiple ways. The ambiguity that is caused by the word alone rather than the context is known as Lexical Ambiguity.
Example: “Give me the bat!”
In the above sentence, it is unclear whether bat refers to a nocturnal animal bat or a cricket bat. Just by looking at the word it does not provide enough information about the meaning hence we need to know the context in which it is used.
Lexical Ambiguity can be further categorized into Polysemy and homonymy.
- a) Polysemy
It refers to a single word having multiple but related meanings.
Example: Light (adjective).
- Thanks to the new windows, this room is now so light and airy = lit by the natural light of day.
- The light green dress is better on you = pale colours.
In the above example, light has different meanings but they are related to each other.
- b) Homonymy
It refers to a single word having multiple but unrelated meanings.
Example: Bear, left, Pole
- A bear (the animal) can bear (tolerate) very cold temperatures.
- The driver turned left (opposite of right) and left (departed from) the main road.
- Pole and Pole — The first Pole refers to a citizen of Poland who could either be referred to as Polish or a Pole. The second Pole refers to a bamboo pole or any other wooden pole.
2. Syntactic Ambiguity/ Structural ambiguity
Syntactic meaning refers to the grammatical structure and rules that define how words should be combined to form sentences and phrases. A sentence can be interpreted in more than one way due to its structure or syntax such ambiguity is referred to as Syntactic Ambiguity.
Example 1: “Old men and women”
The above sentence can have two possible meanings:
- All old men and young women.
- All old men and old women.
Example 2: “John saw the boy with telescope. “
In the above case, two possible meanings are
- John saw the boy through his telescope.
- John saw the boy who was holding the telescope.
3. Semantic Ambiguity
Semantics is nothing but “Meaning”. The semantics of a word or phrase refers to the way it is typically understood or interpreted by people. Syntax describes the rules by which words can be combined into sentences, while semantics describes what they mean.
Semantic Ambiguity occurs when a sentence has more than one interpretation or meaning.
Example 1: “Seema loves her mother and Sriya does too.”
The interpretations can be Sriya loves Seema’s mother or Sriya likes her mother.
Example 2: “He ate the burnt lasagna and pie.”
The above sentence can be interpreted as either ‘the lasagna was burnt and the pie wasn’t’ or both were burnt.
4. Anaphoric Ambiguity
A word that gets its meaning from a preceding word or phrase is called an anaphor.
Example: “Susan plays the piano. She likes music.”
In this example, the word she is an anaphor and refers back to a preceding expression i.e., Susan. The linguistic element or elements to which an anaphor refers is called an antecedent. The relationship between anaphor and antecedent is termed ‘anaphora’. ‘Anaphora resolution’ or ‘anaphor resolution’ is the process of finding the correct antecedent of an anaphor.
Ambiguity that arises when there is more than one reference to the antecedent is known as Anaphoric Ambiguity.
Example 1: “The horse ran up the hill. It was very steep. It soon got tired.”
In this example, there are two ‘it’, and it is unclear to which each ‘it’ refers, this leads to Anaphoric Ambiguity. The sentence will be meaningful if first ‘it’ refers to the hill and 2nd ‘it’ refers to the horse. Anaphors may not be in the immediately previous sentence. They may present in the sentences before the previous one or may present in the same sentence.
Anaphoric references may not be explicitly present in the previous sentence rather they might refer to the part of the antecedent.
Example 2: “I went to the hospital, and they told me to go home and rest.”
In this sentence, ‘they’ does not explicitly refer to the hospital instead it refers to the Dr or staff who attended the patient in the hospital.
Anaphors are mostly pronouns, or they can even be noun phrases in some instances.
Example 3: “Darshan plays keyboard. He loves music. “
In this case ‘He’ is a pronoun.
Example 4: “A puppy drank the milk. The cute little dog was satisfied.”
Here Anaphor is ‘cute little dog’ which is a noun phrase.
5. Pragmatic ambiguity
Pragmatics focuses on the real-time usage of language like what the speaker wants to convey and how the listener infers it. Situational context, the individuals’ mental states, the preceding dialogue, and other elements play a major role in understanding what the speaker is trying to say and how the listeners perceive it.
Example:
I will explain methods to deal with ambiguities in my upcoming blogs till then Happy reading!!!!
Please read my new blog on text preprocessing From Raw Text to Insightful Analysis: NLP Text Preprocessing Explained .
EndNote:
I hope you enjoyed the article and got a fair understanding of different types of linguistic ambiguities. Please drop your suggestions or queries in the comment section.
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