Many people write haiku in three lines, although traditionally Japanese haiku were often written in a single line, and modern haiku writers often write haiku in one, two, three or possibly four lines.
In Japan, haiku were written in seventeen on or onji. The word on in Japanese means sound, and onji means sound symbol. Because of the difference in languages, the use of seventeen syllables in English forms a longer haiku than it would in Japanese language. In keeping with one of the most important rules of haiku – brevity, and to try to approximate Japanese language more closely, it is preferable to write English haiku in approximately twelve syllables, or as few syllables as possible, but not over 17 syllables.
Haiku in Japan usually contains a season word or words (kigo) and a saijiki is used to decide which words relate to which seasons. However, in Australia, because our seasons are different, many don’t use a kigo and try instead to use Australian season references, depending on who their intended audience is. See Australian Haiku Dreaming -http://users.mullum.com.au/jbird/dreaming/ozku.html for more on Australian season references.
Haiku usually has a distinct grammatical break (kireji) between the ‘fragment and the phrase’. Sometimes a dash is used to highlight the kireji, again depending on the intended audience. It is preferable to use one or two clear, contrasting images.
Senryu is similar, except it emphasizes humor and human foibles instead of seasons, and may not use kigo or kireji.
For haiku definitions go to: http://www.haikuoz.org/haiku_definitions/.
Key points on writing haiku
Brevity is a key element in haiku. Around 12 syllables or less is ideal, but up to 17 syllables is okay, as Graham Nunn says, ‘don’t count the syllables, make the syllables count’.
In 1, 2, 3 or possibly 4 lines. Three lines is the most common setting out in English language haiku.
That preferably uses the simplest type of language, avoiding literary or highbrow language. That preferably does not use poetic tools, such as simile, metaphor, rhyming, punctuation (except perhaps a dash to mark a grammatical break), capital letters (except Proper nouns), titles, personification, abstract images and language.
Haiku capture a moment in time, therefore need to be written in present tense. “The magic of haiku is in its simplicity. Haiku is a thing of beauty, a moment transfixed; it is meditation. … The moment is fleeting. … The key to writing a good haiku is to record the moment as soon as possible after the experience, in the present tense and in the least number of words.” Rose Van Son
That preferably infers an awe or a reverence of nature and uses a nature reference, however, some modern haiku doesn’t necessarily refer to nature. “There needs to be an underpinning of reverence, a deep appreciation for the natural world in all its forms, including the human.” Author unknown
That relates to the senses.
Juxtaposition of two images is preferable, but single image haiku is okay as well.
That has an ‘aha’ factor. “That aha moment of realisation, an expulsion of air, often leaves the reader breathless.” Rose Van Son
“The best indicator of a haiku is the break, at the end of the first or second line. Another would be the association, marrying, contrast of two concrete images in a way that is unspoken and allows the reader to make the links.” Author unknown
“A good haiku is a pebble thrown into the pool of the listener’s mind, evoking associations out of the richness of the listener’s own memory. It invites the listener to participate instead of leaving him dumb with admiration while the poets shows off.” Alan Watts