What is semantics?

Semantics is a sub discipline of linguistics which focuses on the study of meaning. Semantics tries to understand what meaning is as an element of language and how it is constructed by language as well as interpreted, obscured and negotiated by speakers and listeners of language.[1]
Semantics is closely linked with another sub discipline of linguistics, pragmatics, which is also, broadly speaking, the study of meaning. However, unlike pragmatics, semantics is a highly theoretical research perspective, and looks at meaning in language in isolation, in the language itself, whereas pragmatics is a more practical subject and is interested in meaning in language in use.
Semantics is the study of meaning, but what do we mean by 'meaning'?
Meaning has been given different definitions in the past.
Meaning = Connotation?
Is meaning simply the set of associations that a word evokes, is the meaning of a word defined by the images that its users connect to it?
So 'winter' might mean 'snow', 'sledging' and 'mulled wine'. But what about someone living in the amazon? Their 'winter' is still wet and hot, so its original meaning is lost. Because the associations of a word don't always apply, it was decided that this couldn't be the whole story.
Meaning = Denotation?
It has also been suggested that the meaning of a word is simply the entity in the World which that word refers to. This makes perfect sense for proper nouns like 'New York' and 'the Eiffel Tower', but there are lots of words like 'sing' and 'altruism' that don't have a solid thing in the world that they are connected to. So meaning cannot be entirely denotation either.
Meaning = Extension and Intention
So meaning, in semantics, is defined as being Extension: The thing in the world that the word/phrase refers to, plus Intention: The concepts/mental images that the word/phrase evokes.[2] 
Semantics is interested in:
  • How meaning works in language:
The study of semantics looks at how meaning works in language, and because of this it often uses native speaker intuitions about the meaning of words and phrases to base research on. We all understand semantics already on a subconscious level, it's how we all understand each other when we speak.
  • How the way in which words are put together creates meaning:
One of the things that semantics looks at, and is based on, is how the meaning of speech is not just derived from the meanings of the individual words all put together, as you can see from the example below.

The Principle of Compositionality says that the meaning of speech is the sum of the meanings of the individual words plus the way in which they are arranged into a structure.
  • The relationships between words:
Semantics also looks at the ways in which the meanings of words can be related to each other. Here are a few of the ways in which words can be semantically related.
 Semantic relationship
 Definition  Example
 Synonymy Words are synonymous/ synonyms when they can be used to mean the same thing (at least in some contexts - words are rarely fully identical in all contexts). Begin and start,
Big and large,
Youth and adolescent.
 Antonyms  Words are antonyms of one another when they have opposite meanings (again, at least in some contexts). Big and small,
Come and go,
Boy and girl.
 Polysemy  A word is polysemous when it has two or more related meanings. In this case the word takes one form but can be used to mean two different things. In the case of polysemy, these two meanings must be related in some way, and not be two completely unrelated meanings of the word. Bright- shining and bright- intelligent. Mouse- animal and mouse- on a computer.
 Homophony  Homophony is similar to polysemy in that it refers to a single form of word with two meanings, however a word is a homophone when the two meanings are entirely unrelated. Bat- flying mammal and bat- equipment used in cricket.
Pen- writing instrument and pen- small cage.
  • The relationships between sentences:
Sentences can also be semantically related to one-another in a few different ways.

 Semantic relationship
 Definition  Example
Paraphrase One relationship that two sentences can have with each other is being paraphrases of each other. This is a good example of how we all understand semantics already on some level because people can easily tell when a sentence is a paraphrase, because when two sentences are paraphrases of each other, even though the form is different you will understand the same meaning from them. Paraphrases have the same truth conditions; if one is true, the other must also be true. 'The boys like the girls' and 'the girls are liked by the boys',
'John gave the book to Chris' and 'John gave Chris the book'.
Entailment Entailment is a little more tricky than paraphrase in that the two sentences don't mean exactly the same thing, instead, when one sentence entails another, for the second sentence to be true, the first one must be true. There are two different types of entailment.  
Mutual enatilment
When each sentence entails the other, i.e. each sentence must be true for the other to be true. 'John is married to Rachel' and 'Rachel is John's wife',
'Chris is a man' and 'Chris is human'.
Asymmetrical entailment
With asymmetrical entailment, only one of the sentences must be true for the other to be true, but that sentence may be true without the other sentence nescessarily having to be true. 'Rachel is John's wife' entails 'John is married' (but John is married does not entail Rachel being his wife), 'Rachel has two brothers' entails 'Rachel is not an only child' (but Rachel not being an only child does not entail Rachel having two brothers).
Contradiction Sentences can also be semantically related when they contradict each other. Sentences contradict each other when for one to be true the other must not be. 'Rachel is an only child' and 'Rachel's brother is called Phil', 'Alex is alive' and 'Alex died last week'.
  • Ambiguity:
One of the aspects of how meaning works in language which is studied most in semantics is ambiguity. A sentence is ambiguous when it has two or more possible meanings, but how does ambiguity arise in language? A sentence can be ambiguous for either (or both!) of the following reasons:
Lexical Ambiguity: A sentence is lexically ambiguous when it can have two or more possible meanings due to polysemous (words that have two or more related meanings) or homophonous (a single word which has two or more different meanings) words.
Example of lexically ambiguous sentence: 'Prostitutes appeal to the Pope'. This sentence is ambiguous because the word 'appeal' is polysemous and can mean 'ask for help' or 'are attractive to'.
Structural Ambiguity: A sentence is structurally ambiguous if it can have two or more possible meanings due to the words it contains being able to be combined in different ways which create different meanings.
Example of structurally ambiguous sentence: 'Enraged cow injures farmer with axe'. In this sentence the ambiguity arises from the fact that the 'with axe' can either refer to the farmer, or to the act of injuring being carried out (by the cow) 'with axe'.[2]
Semantics in the field of Linguistics
Semantics looks at these relationships in language and looks at how these meanings are created, which is an important part of understanding how language works as a whole. Understanding how meaning occurs in language can inform other sub disciplines such as Language acquisition, to help us to understand how speakers acquire a sense of meaning, and Sociolinguistics, as the achievement of meaning in language is important in language in a social situation.
Semantics is also informed by other sub disciplines of linguistics, such as Morphology, as understanding the words themselves is integral to the study of their meaning, and Syntax, which researchers in semantics use extensively to reveal how meaning is created in language, as how language is structured is central to meaning.

To find out about some of the key researchers in semantics please follow this link.