For those who may not have an interest in poetry, I'll explain the Haiku Poetry writing. It is a Japanese form of poetry with three syllables for the first line, seven for the second line and, again, five for the third line. The English word "syllable" isn't quite an accurate translation for the Japanese word describing the style but it comes the closest.
The final line was to be ended with what the Japanese called a "cutting" word - a word that concluded the thought, rather an "aha" conclusion. It wasn't intended to be left hanging incomplete. The English writers took another liberty, if at the end of the poem they didn't have a cutting word, they would use either a dash or an ellipsis to convey the general idea of further thought left unstated.
This form of poetry always dealt with nature and seasons, but as the English began to compose from its model some things were changed from the original. Some choose a different number of syllables per line and some also choose different themes. So far, I've clung to nature and season; I would like to try my hand at social issues, an entirely different theme for sure!