Tanka means Japanese poem. It is longer than a haiku; when it was westernized poems were broken to lines and it had a 5-7-5-7-7 syllable structure. Tanka is not as popular as haiku, but poets do write it. Did you know that some poets write it without any capitalization at all? That's not uncommon in modern poetry, but it always strikes me as funny. Here are some sample Tanka poems.