There exist multiple media for communication, however we do not call all of them a ‘language’. What then is a language?
Charles F Hockett, a famous linguist of the 21st century defined 16 of what he believed were the characteristic “features of language” in the 1960s. A brief description of some of these follows.
Many (but by no means all) human languages and animal communication systems are rooted in the medium of sound (speaking/listening), like birdsong or a lion’s roar. Further, each species’ particular sound is innate, just like human voice is. Animals, however, cannot transfer their vocal-auditory communications to any other medium, the way humans do by writing.
The symbols used to connect the signifier (word) and the signified (objects, concepts) are arbitrary; there is no logical connection between the two, e.g., tree, vriksha, ped.
Animals, on the other hand, generally have a strong link between the message and the signal. For example, among crabs, extending a small claw means it is less angry than if it extends a large claw. However, it may be arbitrary, as in the case of gulls, which express agression by turning away from the opponent and uprooting beakfuls grass.
This is not, therefore, a very critical distinction.
Onomatopoeic words are an exception to the characteristic arbitrariness, since they are formed so that they imitate the sound they represent. However, these are very few in number in any language, and also vary across languages.
Human language is built around the categorization and classification of entities and actions. It uses symbols to refer to specific objects and actions, which are put together to convey a wider meaning. Animal communication, on the other hand, is largely about total situations and not specific details.
For instance, in the sentence “He jumped on the chair”, the words “jumped” and “chair” form self-contained units of meaning independent of the wider context, and can therefore be used whenever the corresponding action or object is referred to. Most animals, however, may have a special call for “danger”, but cannot communicate the much more nuanced sentiment of “run away quickly because a snake is approaching our new nest”. As Bertrand Russell said,
No matter how eloquently a dog may bark, he cannot tell you that his father was poor but honest.
This is a distinctive characteristic of human language. First, we note that the structure and order of units in language is important – arbitrariness does not mean randomness. We all know “A see tree I big can beautiful and” is wrong, while “Can I see a tree big and beautiful?” is right.
Languages organise and combine sounds and arrange words in set ways. The small number of individually meaningless atoms come together to form larger meaningful symbols. From a finite set of such atoms, we can create an indefinitely large number of objects – human language is creative.
Similarly, one root, when affixed, may lead to a large number of different words. The Hindi word chal, for instance, gives rise to chalega, chalna, chalana, chalta, chali, etc.
Human beings are also capable of reacting differently to the same stimulus; that is, utterances are not uniquely related to what is happening in the vicinity. For example, if a group visits the Louvre to see the Mona Lisa, they may all react slightly differently.
Human beings can say anything they like in any context. This includes the saying the wrong thing or lying (deception or prevarication), and speaking about something that has already happened or that is happening elsewhere (temporal & spatial displacement). Animals cannot speak of that which does not exist.