Linguistics is the scientific study of language. It concerns itself with the fundamental question of what language is and how it is related to the other human faculties. It studies language as a uniquely human phenomenon (a cultural, social, and psychological phenomenon) by focusing on what one must know in order to speak/sign and understand language. When there are remarkably diverse means of expression in the languages of the world, many of the features of language are found to be universal. This leads to the understanding that there are universal aspects to human experience and language has a built-in biological basis resulting from evolution. Linguists seek to determine what is unique in languages, what are common elements of all languages, how language is acquired, what kinds of unconscious knowledge humans have about language, how it is represented in the human mind, how it interacts with other mental processes, how language varies from person to person and region to region, how it changes with time and what triggers the changes.