Literature is a creation in which authors employ the linguistic materials   to create the readable valuable artistic language form to present and reflect their   emotion and their response to the life, and whose definition should be defined by the readers.
    1 Literature is a creation.
      1) With purely imagination, some authors use the language to create fabled world, in other words, all the things in story are created by authors’ mind and imagination. Such as the stories about magic or ghost, authors use their imagination to imagine various kinds of magic or different types of ghost.
      2) Some authors are tend to create their works based on the real   world combining with their expansive imagination, in some degree, these creations have surpassed the real.
        a) First, authors’ creation are based on the real. Author will create many different characters and set the story in many different scenes in his novel, all these are based on the real. The characters in the novel are likely to the real person in the real world, like the angel whose face and body is a real portrait of human being except her wing. The characters imitate human being’s completive feeling of happy, of sadness, of sorriness and their clothes are designed depend on real, gentlemen are dress in the gentlemen alike of the social upper class, the poor in shabby clothes is likely to the beggars on the street.
        b) Even though the creation is based on the real, it always surpasses the real in both its life phenomenon and human emotion by associating with their dreaming life. In the knight era, people dared not to against the knight’s will, but they do dare in the novel. And they show their dream of casting down the tyrannized knight to live in peace without any oppression in the novel. (来源：EnglishCN.com)
    2 Literature is the creation whose aim is to present and reflect authors’ feeling and emotion or express their view on something.
Even how great these creations are, they are created by the authors, so what they’ve written are to serve the aim which is to present their feeling and emotion or reflect their view on something. Authors would use letters to express what they thought and felt and to give their hope. In “SONS AND LOVERS”, Laurence told out his hatest to his mother who gave him not only her hope and passion but also her all-possessive affection which becomes a hindrance to his independent development as a man, pouring out his psychological torture in the bottom of his heart. And the main character Paul (symbolized himself) eventually got freedom from his mother’s death and his lovers’ left could be deemed as his hope to his life. Under authors’ pen, the letters are come to life to tell out the authors’ view and response on something. Jane Austin shows her worldview on marriage that is not built on wealth and viscomty, but on spiritual understanding of each other, against the trend of money—based marriage in her great novel “PRIDE AND PREJUDICE”. From it, we might judge what’s Austin’s response to the marriage in the real life.
    3 Literature, this creation’s form is made of the readable valuable artistic language.
It’s not each works that can be identified with the literature even though it is also written to express and reflect writer’s thought and emotion. Only those that employ the readable valuable artistic language to create linguistic form might become literature.
Readable means the form that could be read by others. But what’s valuable language? It refers to that the writers should carefully select different and proper words used by different characters in different occasions. People come from different class use different words, the upper class is deemed to use the elegant words, while the lower use the causal words. Different conversation appears in different occasion, the conversation between friends is different from that between unfamiliar people even though they are discussing the same topic. Even if in the same kind of instance, if it happens in different place, words’ using are also different. For example, the words are used in the party held by a common family is differ from which are used in the party held by the noble family. Proper words appear in proper occasion shows the valuable language using, while using this valuable language to achieve some purpose can reflect the artistic employing of language. Authors will use the valuable language to say something to achieve some purposes, such as to satirize or foil something or give a parable on something.
  The words that are valuable used in the suitable place could be defined as the artistic words.
    4 Literature should be defined by readers.
  Even though the works is to express the authors’ emotion or view on something in some readable valuable artistic language, they still just have the chance to become literature. When we enter in some bookstores, we will found that some books attract more readers, while others have nobody to inquiry. Here refers to the resonance between author and readers. Generally speaking, if the works can affect the readers (here, the readers should include either the contemporaneous or the future readers of the book), or the author’s emotion in it can infect them, or the view can get the resonance from them no matter it’s agree or opposite, it is meaningful, a book without any readers is meaningless. So the literature should be defined by readers.

(My writing is based on my limit knowledge of literature, and the views in it are all my own opinion)