structural:expansion, information:classification
Kiru and kireji

In Japanese haiku, a kireji, or cutting word, typically appears at the end of one of the verse's three phrases. A kireji fills a role analogous to that of a caesura in classical Western poetry or to a volta in sonnets. A kireji helps mark rhythmic divisions. Depending on which kireji 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.

The kireji lends the verse structural support, allowing it to stand as an independent poem. The use of kireji distinguishes haiku and hokku from second and subsequent verses of renku; which may employ semantic and syntactic disjuncture, even to the point of occasionally end-stopping a phrase with a sentence-ending particle (終助詞, shūjoshi). However, renku typically employ kireji.

In English, since kireji have no direct equivalent, poets sometimes use punctuation such as a dash or ellipsis, or an implied break to create a juxtaposition intended to prompt the reader to reflect on the relationship between the two parts.

The kireji in the Bashō examples "old pond" and "the wind of Mt Fuji" are both "ya" (や). Neither the remaining Bashō example nor the Issa example contain a kireji. However, they do both balance a fragment in the first five on against a phrase in the remaining 12 on (it may not be apparent from the English translation of the Issa that the first five on mean "Edo's rain").