I have copied this form https://akitahaiku.com/what-are-haiku-senryu-and-tanka/. The site is Japanese although mainly using english. It may be closing down as it was a 10 year project now completed.
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What are Haiku?
Haiku is a form of Japanese poetry, consisting of 17 morae (or on), in three metrical phrases of 5, 7 and 5 morae respectively. Haiku typically contain a kigo, or seasonal reference, and a kireji, or verbal caesura (cutting word).
English-language haiku poets think of haiku as a Japanese form of poetry generally (but not always) consisting of 17 syllables, usually within three lines, with 5, 7 and 5 syllables.
In Japanese, haiku are traditionally printed in a single vertical line, while haiku in English usually appear in three lines, to parallel the three metrical phrases of Japanese haiku. The essential element of form in English-language haiku is that each haiku is a short one-breath poem that usually contains a juxtaposition of images.
Most haiku writers prefer poems that refer to nature and social events, but some of them don’t always place an exacting seasonal word in the poem. Furthermore, a few of them write haiku composed on one or two lines in less than 17 syllables. Currently the majority of haiku are written in 11 short syllables in a 3-5-3 format.
And Senryu?
Senryu is a Japanese form of short poetry similar to haiku in construction: three lines with 17 or fewer morae (or on) in total. However, senryu tend to be about human foibles while haiku tend to be about nature, and senryu are often cynical or darkly humorous while haiku are more serious. Unlike haiku, senryu do not include a kireji or verbal caesura (cutting word), and do not generally include a kigo, or seasonal word.
It is often said that both haiku and senryu can be funny, but that if it’s funny, it’s probably senryu. Both haiku and senryu can be about nature, but if it’s about nature, it’s probably a haiku. In addition, both haiku and senryu can be about nature or human nature. Both haiku and senryu can be serious or humorous/satirical. A serious poem about nature is certainly a haiku. And a funny/satirical poem about human nature is certainly a senryu.
So what about Tanka?
Tanka consist of five units (often treated as separate lines when transliterated or translated), usually with the following mora pattern: 5-7-5-7-7.
The 5-7-5 is called the kami-no-ku (“upper phrase”), and the 7-7 is called the shimo-no-ku (“lower phrase”).
