Tradition reigned in haiku writing until the 1970s when a variant to the haiku was invented. It became known as the monoku.

The monoku is a one-line poem variation of the haiku. Three writers of poetry in the 1970s made the monoku popular as a form of haiku. They are:

• Marlene Mountain who wrote monoku in horizontal line
• Hiroaki Sato who translated Japanese haiku into one line in English. Sometimes that line is in vertical rather than horizontal form
• Matsuo Allard wrote essays in favor of the monoku form and published several magazines devoted to the form

Monoku is written as a single line which contains seventeen syllables or less. It includes a caesura (a pause) dictated by a sense or speech rhythm with little or no punctuation. The first word in the line is not capitalized and is in lowercase.