What is Language?

Many animal and even plant species communicate with each other. Humans are not unique in this capability. However, human language is unique in being a symbolic communication system that is learned instead of biologically inherited. Symbols are sounds or things which have meaning given to them by the users.

A word is one or more sounds that in combination have a specific meaning assigned by a language. The symbolic meaning of words can be so powerful that people are willing to risk their lives for them or take the lives of others. For instance, words such as "queer" and "nigger" have symbolic meaning that is highly charged emotionally in America today for many people.

A major advantage of human language being a learned symbolic communication system is that it is infinitely flexible. Meanings can be changed and new symbols created. This is evidenced by the fact that new words are invented daily and the meaning of old ones change. For example, the English word "nice" now generally means pleasing, agreeable, polite, and kind. In the15th century it meant foolish, wanton, lascivious, and even wicked. Languages evolve in response to changing historical and social conditions. Some language transformations typically occur in a generation or less. For instance, the slang words used by your parents were very likely different from those that you use today.

A language is a set of rules for generating speech.
A dialect is a variant of a language.

Which language is spoken depends on the social situation.

The dialects of a society are ranked relative to each other in terms of social status.

Source: O'Neil, 2006

Terms that you should look into:

Regional dialect and Social dialect
Pidgins and Creoles