Toodling around on WordPress for the past few days, I keep seeing people writing what they undoubtedly think of as haiku. I got taught what everybody else got taught about haiku in fifth grade English class: a haiku is a Japanese three-line poem, the lines having five, seven, and five syllables, for a grand total of seventeen syllables. Easy-peasy, right? Well, actually, no.
First of all, that description is a definition of a senryu, not a haiku. For the poem to be a haiku, it needs a kigo, a word that refers to the seasons and nature. Also there should be a kireji, a “cutting” word, that is like a caesura (pause) in English poetry. Often, translations of Japanese poems in English will use punctuation like a colon or a period to show the stopping and starting again. Often the first two lines set up an image and the last line pulls the rug out from under the reader or possibly gives the reader something new to appreciate.
Second, syllables in English are very different from syllables in Japanese. The word for teacher, sensei, looks like two syllables to an English speaker, but is in fact four in Japanese, se/n/se/i. This means that while you could feasibly have as many as seventeen words in a seventeen-syllable poem in English, Japanese poets are using very few words indeed.
One of the ways that the classical poets got around this problem was with a kind of poetic shorthand, phrases or tropes that everyone recognized. So, for example, the phrase “wet sleeves” implies the end of a love affair.
One of the uses of these shorter poems (we can talk about tanka, renga and haibun another time) is to write a final farewell poem at one’s death. Often a samurai would write such a poem before going off to battle, as presumably, one fights with more ferocity if one has accepted the possibility of one’s death and prepared oneself for it.
To the Western world, Matsuo Basho (1644-1694) is probably the most well-known and widely quoted Japanese poet. You probably had his frog haiku in your schoolbook just as I did: furu ike ya / kawazu tobikomu / mizu no oto
an ancient pond
a frog jumps in
the splash of water 
I also really like Kobayashi Issa (1763-1828). He is one of the four great haiku masters, along with Basho, Buson and Shiki. Here is one of his poems.
Climb Mount Fuji,
But slowly, slowly!