Since 1905, non-Japanese poets have experimented with writing and publishing haiku in their own languages, and there are now haiku writers in over 50 countries, writing in 25 or more languages.

People writing haiku in English and other languages have used a variety of forms. The four most common today are (1) Seventeen syllables arranged in three lines of five, seven, and five syllables. (This form produces works quite a bit longer in English than their Japanese counterparts; now it is used mostly by classroom teachers and their students with relatively little knowledge of haiku.) (2) Three lines of two, three, and two accented beats, respectively. (This form has been advocated by the British scholar and Zennist, R. H. Blyth, whose four-volume work entitled simply "Haiku" has been the starting point for many students of the genre. Some contemporary poets use it.) (3) A relatively free-form system of three short lines. (This is the dominant form for English haiku today; in the hands of good poets, it becomes akin to the "organic form" of modern American poetics.) (4) One line in from three to 15 syllables, sometimes punctuated, sometimes with space inserted to indicate a pause similar to a line-break. (This form has been advocated by Hiroaki Sato, an important translator of haiku, and has been adopted by several poets writing in English.)

Since many of those writing haiku outside of the Japanese tradition know little about the requirements for haiku in Japanese, many things that do not seem very much like haiku to Japanese poets have been called "haiku" in other languages.

Before haikai no renga there was a more formal style of linked poetry, called "renga". And renga grew out of the tradition of Japanese court poetry, particularly what are today called "tanka" (short poems).

Since haiku, a sort of comic haiku arose in the 1700s, and is now called "senryu".

In addition, there is a variety of prose, often in the form of a diary or journal, called "haibun". Haibun usually contain haiku; a short haibun may be simply a haiku with a paragraph of prose as an introduction.

A senryu has the same form as a haiku, but usually omits the season word and focuses instead on the humor of humanity. Like haiku, a senryu is usually written in the present tense and meant to represent a brief action or tableau.

Today there are both haiku and senryu clubs in Japan, and among expatriate Japanese in Brazil, Canada, and the U.S. The so-called "haiku" written in English and other non-Japanese languages often seem more like senryu to Japanese haiku poets.

Today the popular style of renga perfected by Basho (1644-94), known as "haikai no renga" or "renku", has been taken up by poets writing in other languages. Basho and his disciples usually wrote renku of 36 stanzas (called a "kasen"), and this length remains popular today.

In English, renku usually alternate stanzas of three and two lines each, and a completed renku ranges from twelve to fifty or one hundred such stanzas.

Most Japanese poets observe a sharp distinction between tanka and the other traditional forms (such as haiku, renga, senryu, etc.). In English or other translations from Japanese, these differences may not be so apparent, and today many outside of Japan see tanka as closely related to haiku. Since non-Japanese often experiment with writing in both genres, the two are often published together both in books and on the World Wide Web.