A haiku is a traditional Japanese short poem written in a 5 7 5 syllabic structure and usually broken up into two or three lines. The themes of a haiku often revolve around nature and seasons. To be a proper haiku, it must coform to a certain form:
In Japanese, the haiku must have a structure seventeen onji (Japanese sound symbols) in the order of 5 7 5 syllables. Within English, this isn't necessary because the way English words are formed makes it awkward to fit to this strict definition (there are many one syllable words in English with complex meanings - spring for example) - it just needs to less than seventeen syllables. This restriction is removed for English because it would be possible to make a haiku entirely of seventeen one syllable words which would be too complex for the simplicity of a haiku.
Additionally, each of the lines must be a thought on its own. The separation between lines is done with a kireji (cutting word). This word gives emphasis to a particular thought or part of the poem.
Matsuo Bashô: Frog Haiku
Furu ike ya
mizu no oto
This is one of the most translated Japanese haikus One translation of this poem by Lafcadio Hearn is:
frogs jumped in
sound of water.
In this case, the frog is the season word which references late spring. Here, the translator decided to work to preserve the essence of the Japanese rather than enforce a strict pattern to it.
The cutting word in the poem is ya which separates the poem into two parts - the old pond and the frog itself. ya does not have a specific meaning on its own and can be thought of instead as an exclamation with the concept of "stop and behold".