A message may or may not be articulated. The sense of an unarticulated message is mapped as a whole block onto a perceptible object. Here are some examples of unarticulated messages:

1. waving as a sign of telling farewell
2. aaah! as a sign of great pain
3. [kççç] produced by an infant as a sign of complacency
4. a dog's growling as a sign of readiness for attack.

As may be seen, unarticulated messages are used by animals and humans.

A message composed in a natural human language is articulated. This means that it is composed of more elementary components taken from a code. The following are articulated messages corresponding to the preceding examples in their sense:

As may be seen, the content of a message does not depend on its being articulated; its articulation concerns exclusively the structure of the expression. A message is articulated if it is composed of recurrent units, that is, of elements each of which is a token of a type. Such units can be of two kinds:

1. A unit may carry a certain meaning; then it is a significative (‘meaningful’) unit.²
2. A unit may merely distinguish meanings; then it is a distinctive (‘making a difference’) unit.

For an example, consider the rummy game. The cards display two kinds of units:

1. the ranks, from Ace to King, bearing different values in points;
2. the suits, i.e. the categories Clubs, Spades, Hearts and Diamonds (♣, ♠, ♡, ♢).

In this game (this is different in other games) the ranks are significative, for at the end of a game, their points are totalled according to certain rules to determine the winner. The suits are just distinctive; it only matters to keep them apart; but it does not change the result whether one has a run composed of Clubs or of Hearts.

The double articulation of a semiotic system is its articulation both in significative and in distinctive units. Human speech is doubly articulated. Consider the phrase of .

It consists of three smallest significative units (morphemes):

• run ‘move over a (spatial or temporal) distance’
• -ing active participle
• gag ‘comic effect’

Each of these significative units makes its contribution to the meaning of the complex expression. The significative unit run – i.e. /ɽʌn/ – consists of three smallest distinctive segments (phonemes), viz. /ɽ/, /ʌ/ and /n/.

The smallest significative units are composed of distinctive units. However, both articulations comprise both elementary and complex units: phrases are complex significative units; syllables are complex distinctive units.

Given a unit of speech sound, one cannot tell whether it is significative or just distinctive. The sound unit /gæg/, e.g., is a morpheme in the word gag, thus, significative. It is just a syllable in the word gaggle, thus distinctive. Consequently, significativeness and distinctiveness are functions of semiotic units.

The following diagram completes the example of the double articulation of a linguistic expression:³

The double articulation of human language was first formulated in French by André Martinet (1949). He called it double articulation. It is sometimes translated into English by duality (Hockett 1963). The literal translation double articulation is also used, but open to misunderstandings: First, articulation mostly means the pronunciation of sounds from a phonetic point of view, which has nothing to do with the present topic. Second, language is not actually “doubly” articulated, but instead at two levels.

The following schema shows complexity levels of the double articulation of human language:

All known animal communication systems lack double articulation. Primates, too, use unarticulated systems. Their code comprises a set of messages with meanings like ‘Don't get too close!’, ‘Buzz off!’, ‘A raptor is approaching!’. The signals coding these messages are globally distinct; there is no correspondence between parts of a message and parts of a signal. Such a code does not allow the formation of a new message. A semiotic system possessing effability must have double articulation. In the evolution of human language, the formation of double articulation was the decisive feat.

¹ The following notation convention obtains: text in italics is composed of expressions of a specific language; ‘text in quotes’ represents the meaning of an expression.

² Significative is ‘bearing meaning’, as opposed to ‘having no meaning’. (Significant is ‘important’, as opposed to ‘negligible’.)

³ The symbol ‘•’ represents the syllable boundary.