I am not familiar with tankas but a haiku is a three lined poem which the first line has five syllables, the second has seven, and the third has five again. It does not need to rhyme.
A tanka is a five-line poem with a syllable structure of 5-7-5-7-7. To write one, draw inspiration from a personal experience or nature, focusing on specific details. An example of a tanka is included to illustrate this form.
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