Haiku is a Japanese form of poetry, short in size and focused on depiction, vision, and senses, often linked to weather, seasons and observation of nature.  

This Japanese literary form does not contain rhyme or a plot that develops through the course of the poem. 

Haiku’s rhythmic structure is widely known around the world even in the communities that do not have prominent haiku artists. The 5-7-5 morae structure is the core principle of haiku. Each writing consists of three lines with 17 morae overall.

Mora, a phonological unit, closely resembles syllables, as it is known in the Western world. The differences of languages and syllable counting make it difficult to provide a worthy translation of haiku that would convey the content and replicate the 5-7-5 structure.

There is a shorter version of haiku with 11 morae, split between phrases that consist of 3, 5 and 3 morae respectfully. 
Haiku includes a pivotal aspect to every poem written in this form, called kireji. Kireji can be translated as a “cutting word”. Such word in the poem signifies a swift transition from one phase of haiku to another, intentionally causes readers to experience a wide range of emotions, depending on the setting, environment, and meaning of kireji. Literary importance of kireji is hidden in the juxtapositioning of the elements, which colors the rapid transition in a certain verbal punctuation pattern that is suitable for the given haiku. 
To evoke a particular set of thoughts from the reader, haiku artists broadly use kigo, the seasoning word. Kigo is responsible of creating a picture of the time period in the mind. Those periods range from times of year like winter and summer to daily occurrences like dawn or dusk. Kigo is often taken from the saijiki, a list of the seasonal terms contents of which are used in haiku and other related poetic forms. 

The term “haiku” emerged in the late 19th century. Masaoka Shiki, the last of four masters of short Japanese poetry decided that haiku should be a standalone type of poetry and differ from the other ones. He was the one that made the term “haiku” popular in Japan and later overseas. 

Hokku, the predecessor of haiku, experienced its golden period earlier, during the activity of Matsuo Basho, the most famous Japanese poet whose writings are from the Edo time period. These 2 hundred years from 1608 to 1868 are remembered in the history of Japan as the centuries of economic prosperity and the thriving of culture, including poetry. Hokku was used by a vast number of people. 

Its small size and relatively little effort required to complete were the main things that ensured the huge popularity of hokku among the common folk. Strong cultural heritage was passed on by generations and became one of many things that highlight Japanese national identity. 

Core rules of haiku were affected by changes initiated by the cultural progression. While examining closely the works of Masaoka Shiki, it becomes visible that the rule of 17 morae is often neglected. So is the seasoning effect, which becomes substituted for another topics, uncovering the potential variety of possible haiku topics. In the second half of 20th century, after the World War II, haiku became known abroad and influential English Imagists together with other artists started the experiments. It was the time when English haiku was born as a genre. Western artists introduced even more loose and reformed interpretation of classic haiku and introduced a range of new aspects. It drifts away from the style of observing the nature and highlighting the emotions caused by a season, introducing daily, more grounded topics as well as the niche of personal feelings about other individuals, transforming the lone differences in the classic haiku into a fully-developed place of literary operations for the writers. This westernization encourages literary flexibility and assists in popularizing the genre among the beginning artists.