Japanese classical poetry form. It originated from the "faju" in long renga and haiku renge. In the Edo period, due to the advocacy of Matsunaga Sadoku and others, it gradually became independent and added words and phrases related to the four seasons to become a new kind of poetry. Style, this is the earliest haiku. The basic rules of haiku are: Each haiku consists of 17 syllables, and these 17 syllables are divided into three segments: five, seven, and five***. In Japanese, a syllable is not equal to a content word, so a haiku is actually composed of only a few words and can be said to be one of the shortest metrical poems in the world. In addition, each haiku must have a "season title", which is a symbol and hint related to the four seasons, so that readers can understand at a glance which specific season they are chanting. A haiku cannot have more than two quarter titles. Haiku often uses symbols and metaphors, advocating simplicity and implicitness, and is more concise than waka. Matsuo Basho, known as the "Hai Sage", is the most famous haiku author.