# Semantics

[https://en.wikipedia.org/wiki/Semantics](https://en.wikipedia.org/wiki/Semantics)

math :: theory of computation :: terms

Semantics (from Ancient Greek: σημαντικός sēmantikós, "significant") is the study of meaning, reference, or truth. The term can be used to refer to subfields of several distinct disciplines including _mathematical logic_, _linguistics_, _philosophy_, and _computer science_.

## Linguistics

In linguistics, semantics is the subfield that studies meaning. Semantics can address meaning at the levels of words, phrases, sentences, or larger units of discourse. One of the crucial questions which unites different approaches to linguistic semantics is that of the relationship between form and meaning.

## Philosophy

In modern philosophy, the term "semantics" is often used to refer to linguistic formal semantics, which bridges both linguistics and philosophy. There is also an active tradition of metasemantics which studies the foundations of natural language semantics.

## Computer Science

In CS, the term "semantics" refers to the meaning of language constructs, as opposed to their form, which is the domain of syntax. Semantics provides the rules for interpreting the syntax which do not provide the meaning directly but constrains the possible interpretations of what is declared.

### Programming languages

The semantics of PLs is an important area of study in CS. Like the syntax of a language, its semantics can be defined exactly.

PLs use different syntax to describe things, which nevertheless amount to the same (the statements have the same meaning). For example, syntax for addition uses different statement across many PLs but means the same in each one.

The 3 major ways to describe the semantics of a PL formally, by building on mathematical logic are:

* _Operational semantics_: The meaning of a construct is specified by the computation it induces when it is executed on a machine. In particular, it is of interest how the effect of a computation is produced.
* _Denotational semantics_: Meanings are modelled by mathematical objects that represent the effect of executing the constructs. Thus only the effect is of interest, not how it is obtained.
* _Axiomatic semantics_: Specific properties of the effect of executing the constructs are expressed as assertions. Thus there may be aspects of the executions that are ignored.

### Semantic models

The **Semantic Web** refers to the extension of the World Wide Web via embedding added _semantic metadata_, using _semantic data modeling_ techniques such as _Resource Description Framework (RDF)_ and _Web Ontology Language (OWL)_.

On the Semantic Web, terms such as _semantic network_ and _semantic data model_ are used to describe particular types of data model characterized by the use of directed graphs in which the vertices denote concepts or entities in the world and their properties, and the arcs denote relationships between them.

These can formally be described as _description logic_ concepts and roles, which correspond to OWL classes and properties.

[https://en.wikipedia.org/wiki/Category:Programming\_language\_semantics](https://en.wikipedia.org/wiki/Category:Programming_language_semantics) [https://en.wikipedia.org/wiki/Semantics\_(computer\_science](https://en.wikipedia.org/wiki/Semantics_\(computer_science)) [https://en.wikipedia.org/wiki/Computational\_semantics](https://en.wikipedia.org/wiki/Computational_semantics) [https://en.wikipedia.org/wiki/Formal\_semantics\_of\_programming\_languages](https://en.wikipedia.org/wiki/Formal_semantics_of_programming_languages) [https://en.wikipedia.org/wiki/Semantic\_equivalence](https://en.wikipedia.org/wiki/Semantic_equivalence) [https://web.archive.org/web/20150619164601/http://www.emu.edu.tr/aelci/Courses/D-318/D-318-Files/plbook/semantic.htm](https://web.archive.org/web/20150619164601/http://www.emu.edu.tr/aelci/Courses/D-318/D-318-Files/plbook/semantic.htm)
