Senryu?

[Brownlie]

yes it's called a juxtaposition and usually it works with two abstracts,

in the haiku, the cutting word is used as punctuation, ie a Caesura or period. the haiku has two contrasting images both

from wiki (cos it was the easiest )

A kireji fills a role somewhat analogous to a caesura in classical western poetry or to a volta in sonnets. Depending on which cutting word is chosen, and its position within the verse, it may briefly cut the stream of thought, suggesting a parallel between the preceding and following phrases, or it may provide a dignified ending, concluding the verse with a heightened sense of closure.

i understand what you're saying about a statement of the main metaphor in a sonnet

unlike the sonnet, the haiku has no main metaphor for the cut to make a statement about about. it plays one image of another; this line is just conjecture on my part based on what i've been reading on haku and i do realise or think you have a much greater knowledge of poetry compared to mine.

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ihave to piss off for now but thanks for the input milo. i'll do a bit more reading on the subject

I think Jack Kerouac did a book of haikus, it might be worth checking out.