The dodoitsu is a poem form from rural Japan originating in the late Edo Period. In Western execution, the poem is characterized as having a syllable structure of 7-7-7-5. The form is similar to the much more popular haiku, in that the syllable count is the primary metric, with no rhyme specific scheme or meter.
A tanka is a short Japanese free verse consisting of 31 syllables. While they don’t necessarily rhyme, tankas follow a specific syllable pattern. Tanka literally means “short poem or song”, with themes that are usually about nature, seasons, and desires. Hence, tankas tend to evoke strong and powerful imagery.