Couplet is the derivative of Chinese characters and literature and is unique in the Chinese language. It's an art related to both the Chinese language and Chinese characters or we can say that if there were no Chinese characters, couplet would not exist.

Couplet, also called Pillar Posters or Antithetical Couplet, is a pair of lines of poetry that are usually rhymed.

Couplet comprises of a couplet written on vertical strips of red paper in the best calligraphic style one can master. The first (called upper) line is posted on the right side of the front door. The second (called lower) line is posted on the left side of the front door. In addition, a third horizontal piece may be posted across and on top the door.

Couplet falls into three categories according its functions -- for practical use, for decoration and for improvement of language skills.

Couplets for practical use include spring couplets, which are a pair of sayings that offer good wishes at the beginning of the New Year and usually painted on red paper and are pasted on walls close to each other, and couplets used in social intercourse such as marriage couplet, longevity couplet, greeting couplet and elegiac couplet.

As for couplets for decoration, it covers two types -- indoor type and outdoor type, both of which are posted on principal parts of architectures.

Couplets for improvement of language skills vary a lot from one to another and one of their characteristics is that they should meet certain special requirement(s). This type of couplet includes proper noun couplet, cento and palindrome couple.