When written in English, tanka poems must meet criteria concerning their structure and content. Regarding structure, the first line of a tanka poem has five syllables, the second line has seven syllables, and the third line again has five syllables—a pattern also found in haiku poetry. A tanka poem deviates from a haiku poem, however, with fourth and fifth lines that are each seven syllables. The number of syllables in each line is the only stylistic constraint of tanka. The fourth and fifth lines give it a spiritual twist.