Note: the text of this document originally appeared as a Usenet post to the writing newsgroup, misc.writing.
Cutting words are verbal exclamations. They punctuate and emphasise the end of a haiku section. I should note at this point that, traditionally, Japanese haiku is written in one line. Thus, the cutting word will signal the end of one of the three segments.
I'm reading a great book right now that has good examples of the sound lengths in it. Let me dig it out ...
Here's one I like. This is from "A Zen Wave: Basho's Haiku & Zen" by Robert Aitken; Weatherhill; New York: 1978; page 43. In this book, Aitken gives his translation of Basho's work, the Romanised Japanese version and a literal translation.
When worn out
And seeking an inn:
yado karu koro ya
fuji no hana
inn seek when!
wisteria of flowers.
You can see in the Romanised Japanese that there is a syllable/sound scheme of 5-7-5. (Note: Romanised Japanese is far more phonetically 'correct' than the English language is.) Because of the final line, Aitken's translation appears to not follow any sort of syllable/sound scheme. However, had the vision been of plum blossoms, you can well imagine the scheme it would be: 3-5-3.
As for the kigo, or season, word, this example works well. The kigo word is wisteria. Incidentally, kigo are not 'required' in senryu. Senryu is a poetry form similar to haiku but different in content. Haiku should reflect the nature of the universe (to be vague about it) while senryu can be more current. It can address political issues, etc. There is a good definition of the differences between senryu and haiku at http://www.ori.u-tokyo.ac.jp/~dhugal/senryuu.html .
Also, haiku will generally have what is called a 'cutting word.' In the example above, the cutting word is 'ya'. Probably some people are already familiar with this word, as it is often used in the names of Japanese restaurants ... some around my home are Nagasaki-ya and Osaka-ya. Quite often, the cutting word is 'translated' as punctuation. In the original Japanese, it signals a break in the line of thought. So, in this particular haiku, Basho, on one of his many pilgrammages, is quite literally exhausted. Who hasn't been there? You're on the road, you're weary and all you want to do is find a hotel/motel where you can crash for the night. And just at that moment, you see something of such incredible beauty that all else is forgotten, if only for a moment. 'Ya' in this poem moves the reader from the weary existence to the beauty. There is no cutting word in Aitken's translation.