Japanese haiku poets often use a book called a saijiki, which lists kigo with example poems. An entry in a saijiki usually includes a description of the kigo itself, together with a list of similar or related words, and some examples of haiku that include that kigo. The saijiki are divided into the four seasons (and modern saijiki usually include a section for the New Year and another for seasonless (muki) words). Those sections are divided into a standard set of categories, and then the kigo are sorted within their proper category. The most common categories (with some examples of Japanese summer kigo) are:
Summer
- The Season: midsummer, dog days
- The Sky and Heavens: drought, rainbow, the Pleiades at dawn
- The Earth: waterfall, flood, summer field (i.e. the abundance of summer wildflowers)
- Humanity: midday nap, sushi, sunbathing, nudity, swimming pool
- Observances: Boys' Day (May 5), A-Bomb Anniversary (August 6)
- Animals: jellyfish, mosquito, snake, cuckoo
- Plants: lotus flower, orange blossoms, lily, sunflower
Although haiku are often thought of as poems about nature, two of the seven categories are primarily about human activities (Humanity and Observances).
Read more about this topic: Kigo