Oxford Dictionary defines Ambiguity as ‘a word or statement that can be understood in more than one way’. Ambiguities aren’t common in our speech, often understood based on the context of the phrase. However when we are parsing a sentence in a computer, ambiguities can occur which might seem obvious to humane. In today’s post we will discussing these types of Ambiguities that occur in a sentence.

Lexical Ambiguity

Lexical Ambiguities are single word ambiguity, where the word can be treated as different part-of-speech tag (noun, pronoun etc.) Let us consider the word silver to understand this ambiguity. In the below sentences we can see that the word silver can occur in more than one form thus leading to confusion when parse a sentence having the silver in it.

• She bought silver ornaments. Here, silver is a noun.
• She made silver speech. Here, silver is a adjective.
• Work pressure had silvered his hair. Here, silvered is a verb.

Syntactic Ambiguity

Syntactic Ambiguities occur in sentences which can be interpreted in more than one way. This is because the sentence can result in more than one parse trees (discussed below). Let us consider the following sentence to understand this ambiguity better.

The confusion here is whether I shot an elephant while wearing my pajamas or if I shot an elephant that was wearing my pajamas. Both interpretations will have completely different parse tree. A parse tree is a syntactic tree which shows the structure of the sentence based on some grammar rules.

Figure 1. Parse Trees for Syntactic Ambiguity (Source www.nltk.org)

One of the major drawbacks of using sigmoid activation function is that for very high or low values of X, the change in prediction is insignificant which may lead to vanishing gradient problem as the derivative of sigmoid function will be very close to zero.

Semantic Ambiguity

These kind of ambiguities occur when the meaning of the word or phrase can be misinterpreted. Such ambiguities might become clearer with context. Let us consider the sentence “We saw her duck”. We don’t know whether they saw her bird or the action of ducking.

Anaphoric Ambiguity

Anaphoric Ambiguity, as the name says, occurs when we use an anaphora entities in a sentence. Anaphora is the reference to entities mentioned previously in the discourse. Let us consider the example “The horse ran up the hill. It was very steep. It soon got tired” Here the first it refers to the hill whereas the second it refers to the horse. However we know this based on world knowledge that we have, which is often not the case when we rely on computers.

Pragmatic Ambiguity

Pragmatic Ambiguity occurs when the sentence can be interpreted in multiple ways due to sentence being not specific and the context not clarifying the true meaning of the sentence. Let us consider the the sentence “I like you too”, it can have multiple interpretations based on the previous dialogue exchange, like I like you the same way you like me, I like you just like someone else does.