Sign

A sign is a collection of signals that together have specific meanings given the proper context, such as that of a language.

A sign can itself be composed of other smaller signs that have meanings on their own but that together convey a different meaning. These smaller signs can similarly be composed of other even smaller signs, but ultimately the smallest of signs will be composed of signals.

For example, the sign "Bagdad" is a word composed of the letters B, a, g, d, a and d. The letters are also themselves signs whose meanings point to the letter's distinct features and roles. We could further break down the letters into the strokes that compose them, but in this alphabet we can't say the strokes are signs because they carry no meaning on their own. Finally, we can break down the strokes into the signals that transmit them, such as the light emitted by a screen or reflected by the ink on a piece of paper.

The word "Bagdad" also has a pronunciation, and this pronunciation has the written form "Bagdad". These are both completely independent signs that, through the rules of the language in which they exist, can be mapped back and forth to each other.

    Signal ---> Sign ---> Meaning ---> Entity

Both of these signs point to various meanings: there are cities, books and songs with the name Bagdad. Namely, however, the capital of Iraq is the most proeminent meaning associated with this sign, and therefore is the meaning that most likely it will transmit.

The process of perceiving the signal, discerning it as a sign, seeking a meaning for it and then evaluating how it fits into a given context is one of the main functions of cognition.