Why are China's ancient poems more than five words and seven words, but less than four words and six words?

Because it was very popular at that time, hehe! The Book of Songs Picking Wei. It's a four-character poem. Heze also has rhyming six-character poems. Among China's voluminous ancient poems, five-character poems and seven-character poems are as magnificent as the surging Yangtze River and Yellow River, attracting the fascination, admiration and heartfelt research of countless literati. However, that six-character poem is like an ordinary stream that is not well known. Although it is also fluid, it can't play a grand movement and show a magnificent scene, so it is left out to the point where few people take care of it. But this originated from the Han and Wei Dynasties. Zhu's two groups of poems discuss the differences in artistic functions between six-character quatrains and five-character quatrains. The first group of poems is "Four Seasons Scenery painted between the walls of Wangliushan Pavilion, each with its own profound meaning. Because the six characters are absolutely unique, five words and four chants are written on the topic of sentences":

There are no valleys in Yunfu, Ran Ran, but there are many hidden rocks. History gave a banquet and sat down, and pedestrians were lost in the snow.

Raise your head up the mountain to vent clouds. Clouds and trees under your feet. I don't know whether spring is shallow or deep, but I see clouds coming and going.

The sunset is in Xifeng and the evening valley is in Nanling. I'm bored and depressed. I'm here to clear the night scene.

The clear autumn is bleak, and the water collapses at night. Since the stone is interesting, no one said anything.

Very omniscient, dense snow turns thousands of forests. Pimaguan mountain road, who knows the customer?

These two groups of poems "try to show their understanding of the artistic traditions and effects of these two different poetic styles by comparing and contrasting the six-character style and the five-character style: namely, the six-character style is suitable for * * *, and the five-character style is suitable for diachronic linear narration; Six words are more suitable for static description and five words are more suitable for dynamic expression; Six words are better than one lettering. You can refer to these.