A human language is a language that has come into existence for the primary purpose of communication between humans. This type of language can evolve naturally or can be constructed intentionally, but in all cases its defining characteristic is its use for communication between humans. In contrast, animals can also be said to have languages, and language is necessary to the functions of some machines. Human language is generally thought to operate in different ways than these other types of language.
The evolution of human language is complex, and there are many different theories on how language developed. Almost all humans acquire one or more human languages as children and can be said to be native speakers of those languages. While there are many different languages, each language is equally valuable for communicating thoughts, though the languages may do so in different ways. Human languages can be very different in terms of grammar and sounds, but their purpose is the same across human cultures.
One of the unique features of human languages is that the connection between sounds and the ideas those sounds represent is arbitrary. Different words can be used to represent the same concept with equal utility, and it is often the case that words are very different between languages. Languages may be interrelated and historically connected, but this does not imply that all languages evolved out of a single original language. Even so, many early studies of human language were concerned primarily with tracing the roots language back to a single original source.
A human language can have many different forms and facets. For example, there may be written and spoken components as well as other ways of encoding the language, such as manual signs. In certain cases, language is not only used for practical communication, but also to differentiate between groups of people, as being able to communicate was once a major sign of intelligence. Language has many social elements when used by humans, and many important aspects of language do not relate to the sounds of the language.
Interestingly, human language is not always used for communication with other humans and in some cases is incorporated into other languages. For example, the type of speech used to command dogs draws from human language but cannot be used by both parties for full communication. The study of languages is constantly evolving, in part because the way in which humans acquire language and even the origin of language is not fully understood. As such, it is impossible to fully define human language, as the subject is still hotly debated.