A seventeen-syllable poem is a type of Japanese poetry known as HAIKU. HAIKU is composed of three lines, with the first and last lines having five syllables each, and the middle line having seven syllables. The content of HAIKU is usually focused on nature and the seasons, and often includes a 'cutting word' or kireji, which marks the transition between the two parts of the poem. HAIKU is a popular form of poetry, and is often used to express feelings of joy, sorrow, or nostalgia.