A haiku and a senryū share the same short three-line, unrhymed shape, traditionally 5, 7 and 5 syllables, but they differ in subject. A haiku is generally tied to a season and a moment of observing the natural world, while a senryū looks at human nature instead, such as family life, work, courtship and everyday foolishness, usually in a satiric or ironic tone.
Senryū began in the 1750s in Edo (now Tokyo). The form is named after Karai Senryū, the pen name of Karai Hachiemon, who judged comic verse contests and helped compile the first volume of the anthology Haifu yanagidaru in 1765. Many senryū poke fun at a victim, and that victim is often the poet.
Source: Academy of American Poets, “Senryū” (Glossary of Poetic Terms)
Image: Two women on a summer evening, a print from the Haifu yanagidaru series (c. 1788–1792), Rijksmuseum, CC0, via Wikimedia Commons.