In Chinese poetry, an antithetical couplet is a pair of lines of poetry which adhere to certain rules (see below). It is also called a chunlian, duilian and spring couplet.
Outside of poems, they are usually seen on the sides of doors leading to people's homes or as hanging scrolls in an interior, and often during Chinese new year as a type of fai chun (festive decoration), expressing hope towards the new year.
Although often called antithetical couplet, they can better be described as a written form of counterpoint. The two lines have a one-to-one correspondence in their metrical length, and each pair of characters must have certain corresponding properties. A couplet is ideally profound yet concise, using one character per word in the style of Classical Chinese.
A couplet must adhere to the following rules:
1. Both lines must have the same number of Chinese characters.
2. The lexical category of each character must be the same as its corresponding character.
3. The tone pattern of one line must be the inverse of the other. This generally means if one character is of the level (平) tone, its corresponding character in the other line must be of an oblique (仄) tone.
4. The last character of the first line should be of an oblique tone, which forces the last character of the second line to be of a level tone.
5. The meanings of the two lines must be related, with each pair of corresponding characters having related meanings too.