To appreciate haiku it is necessary to acquire a taste for it. The first time I tried Japanese Green Tea I thought it very odd stuff. Most Westerners I know have had a similar reaction. I’m used to Green Tea by now but I’m still intrigued by the difference between Green Tea and English Tea. How can they both be tea? How can haiku and what-we-call-poetry both be poetry?
In Japan …
A haiku is a short poem which contains a season-word (a conventional reference to the season of composition) and usually also a cutting-word (spoken punctuation marking a caesura). The typical form is 5-7-5 Japanese syllables although variations are commonplace. Most haiku are best read as being in the present tense. The typical subject matter is nature, or nature linked with human nature. The tone is sincere, usually detached.
A senryu is a poem to the same 5-7-5 pattern as haiku but lacking the seasonal reference. The subject matter is social comment, usually presented as comedy. The tone is ironic.
A tanka is a poem to a pattern of 5-7-5-7-7 syllables. Seasonal references are common but not obligatory. The typical subject matter is human relationships, with feelings often being expressed by the use of natural imagery as an “objective correlative”. A minority of tanka more closely resemble lengthy haiku, with a purer focus on nature. The tanka allows for a greater subjectivity than haiku, with more “poetic” diction. The tone is passionate.
A renku or renga is a series of linked poems built into one long poem, written in co-operation by a group. The pattern is alernating links of 5-7-5 and 7-7 syllables. There is an elaborate framework of conventions governing the placement of seasonal verses and other kinds of content. The overall aim is not narrative but a scattered mosaic covering a wide range of subjects and employing a variety of tones.
Historically, tanka came first (8th century). Renga grew out of tanka (13th century). Haiku grew out of renku (16th century) and senryu grew out of haiku (18th century).
All the above criteria are negotiable. The central quality of all traditional Japanese poetry is its focus on the image. Japanese poetry works by implication, presenting images and relying on the reader to make the interpretations. The poet avoids intruding into the poem. In attempting to imitate Japanese forms it is this technique which English haiku writers hold to be paramount. Most English haiku (etc) are written as free verse because the formal requirements of Japanese genres are impossible to accurately replicate. 17 Japanese syllables do not equate to 17 English syllables. For example, haiku itself has 2 syllables in English, but 3 in Japanese (ha-i-ku).
— Martin Lucas