Semantics (from Ancient Greek: σημαντικός sēmantikós, "significant")[1][2] is the study of meaning. It focuses on the relation between signifiers, like words, phrases, signs, and symbols, and what they stand for, their denotation. Linguistic semantics is the study of meaning that is used for understanding human expression through language. Other forms of semantics include the semantics of programming languages, formal logics, and semiotics. In international scientific vocabulary semantics is also called semasiology.Semantics is the study of the meaning of linguistic expressions. The language can be a natural language, such as English or Navajo, or an artificial language, like a computer programming language. Meaning in natural languages is mainly studied by linguists. In fact, semantics is one of the main branches of contemporary linguistics. Theoretical computer scientists and logicians think about artificial languages. In some areas of computer science, these divisions are crossed. In machine translation, for instance, computer scientists may want to relate natural language texts to abstract representations of their meanings; to do this, they have to design artificial languages for representing meanings.

There are strong connections to philosophy. Earlier in this century, much work in semantics was done by philosophers, and some important work is still done by philosophers.

Anyone who speaks a language has a truly amazing capacity to reason about the meanings of texts. Take, for instance, the sentence

(S) I can't untie that knot with one hand.
Even though you have probably never seen this sentence, you can easily see things like the following:

The sentence is about the abilities of whoever spoke or wrote it. (Call this person the speaker.)
It's also about a knot, maybe one that the speaker is pointing at.
The sentence denies that the speaker has a certain ability. (This is the contribution of the word ‘can't'.)
Untying is a way of making something not tied.
The sentence doesn't mean that the knot has one hand; it has to do with how many hands are used to do the untying.
The meaning of a sentence is not just an unordered heap of the meanings of its words. If that were true, then ‘Cowboys ride horses’ and ‘Horses ride cowboys’ would mean the same thing. So we need to think about arrangements of meanings.

Here is an arrangement that seems to bring out the relationships of the meanings in sentence (S).

Not [ I [ Able [ [ [Make [Not [Tied]]] [That knot ] ] [With One Hand] ] ] ]

The unit [Make [Not [Tied]] here corresponds to the act of untying; it contains a subunit corresponding to the state of being untied. Larger units correspond to the act of untying-that-knot and to the act to-untie-that-knot-with-one-hand. Then this act combines with Able to make a larger unit, corresponding to the state of being-able-to-untie-that-knot-with-one-hand. This unit combines with I to make the thought that I have this state -- that is, the thought that I-am-able-to-untie-that-knot-with-one-hand. Finally, this combines with Not and we get the denial of that thought.

This idea that meaningful units combine systematically to form larger meaningful units, and understanding sentences is a way of working out these combinations, has probably been the most important theme in contemporary semantics.

Linguists who study semantics look for general rules that bring out the relationship between form, which is the observed arrangement of words in sentences and meaning. This is interesting and