Senryu poetry came from thirteenth century Japan, a spinoff of another Japanese form of poetry far more popular at the time, the renga, orally composed by poets in groups. Renga poets would often play a game of showmanship, with one poet offering a stanza of renga off the top of his head and another challenging the previous poet's cleverness by producing something even more compelling. In time, the products of these games became regarded as a new form, senryu poetry that, with a little wit, can be both quick and fun to write.
Like haiku, senryu are often thought to require seventeen syllables, with five syllables in the first line, seven in the second and the final five in the third. However, when writing these kinds of poems, traditional Japanese poets didn't actually count syllables, but sounds. Contemporary linguists tell us that the seventeen sounds of a traditional Japanese senryu actually translate to somewhere between 12 to 15 English syllables. In order to produce a contemporary English senryu, you compose a poem of three brief lines, with the first and third lines a little shorter than the second.
Many traditional senryu focus on awkward romances, confused children and other scenes that allow the poet to poke fun at human nature. One poet writes of a child searching for his shoes, unable to find them because they are on his feet. Another poet writes of a man squinting to read the word "optician." The object of this form is to offer the image of a human in action, doing something relatable, familiar, ironic or even embarrassing. When writing senryu, you could choose moments from your own life that have caused you, or others, to giggle.
Perspective and Tone
Senryu poems do not explore human nature by looking outward at the natural world, but makes the human, not the world around him, its subject. As might be expected from a poem that was first achieved through teasing and game-playing, the tone of the senyru is always humorous, sometimes even sarcastic. The condensed, simple language and the accessibility of haiku is also present in senryu and when writing these poems, you must be direct and explicit. Above all, you must aim to make people laugh.
Learn by Reading
The best way to get a feel for senryu is to read as many of these poems as possible to see what other poets and translators have done, paying attention to the choices they made regarding subject, voice and tone, imagery, diction and syntax. Once you feel you know how a senryu should look and sound, write one or several of your own, expressing your own outlook on life and your own sense of humor.