The number of words in the upper and lower couplets is equal. There are at least 4 words in each couplet, most of which are 7 words, and those with more than 12 words are called long couplets, which are relatively few, and they are flat, that is, flat, which is harmonious and won't be awkward. But the single digits can be arbitrary, and the two digits must be strictly observed. This is called "135 no matter, 246 is clear"
Part of speech is relative. Generally speaking, it is function words versus function words (even if it is not enough, etc. ) and content words to content words. The number of function words is very small, while the number of content words is the largest. For example, noun to noun, verb to verb, adjective to adjective, quantifier to quantifier. If the nouns can be subdivided, it will be more neat, such as the name belongs to the name, the land belongs to the ground, astronomy belongs to astronomy, color belongs to color, beast belongs to beast and so on. As for the choice of words, any words used in the first half can't be used in the second half.
Sticking couplets also has rules, but it is relatively simple. The upper part is attached to the left and the lower part is attached to the right. How to distinguish between up and down links? Tell you a secret. The last word is silent, it must be the upper part, and the last word is flat, it must be the lower part. If the banners are mostly auspicious or inspiring, stick them above the door. There is no need for horizontal approval.
The antithesis between couplets and regular poems has a relationship of inheritance and evolution, and the flat rhythm of regular poems and the principle of "whether one, three, five, two, four or six are clear" are also applicable to couplets. As for the number of words in each couplet, there is no limit, ranging from four words, five words, six words, seven words, eight words and nine words to tens or hundreds of words, as long as you have something to say.