Traditional Haiku Structure
Traditional haiku are always the same, including the following features:

There are only three lines, totaling 17 syllables.
The first line is 5 syllables.
The second line is 7 syllables.
The third line is 5 syllables like the first.
Punctuation and capitalization are up to the poet, and need not follow rigid rules used in structuring sentences.
A haiku does not have to rhyme, in fact usually it does not rhyme at all.
Some haiku can include the repetition of words or sounds