Haiku (plural: haiku) is a short (having no more than four lines) nature-oriented poem expressing the poet’s direct experience of something, description of background/surroundings, and an original and deep thought based on it. It more often than not contains a reference to a certain season or a kigo / season word, one per poem. A proper haiku consists of two distinctive parts and not of one or three. The same goes for one-line haiku, sometimes called monoku.The form of 5-7-5 can be used but is not essential. No title should be given to a haiku.

In haiku writing, verbs are used only in the present or past continuous tenses. It is best to avoid direct metaphors, conditional clauses, e.g., subjunctive mood, end rhymes, and the usage of capital letters and punctuation marks, unless the latter are necessary. Also to be avoided is the usage of adverbs, pronouns, and excessive adjectives, e.g., two of them with the same noun, as well as of too many ‘ing’ words (usually no more than two per poem.) Articles (‘a’ and ‘the’) are usually varied in a particular haiku.

Haiku poets traditionally use only common language and avoid turning their haiku into an aphorism or an epigram. They write about what they see or have seen and avoid writing hearsay haiku. Brevity is the essence of haiku poetry, so it is best to remove any words that can be removed without losing the sense of the piece. Best haiku possess such qualities as lightness, simple beauty, unexpectedness, elegance, refinement, and drifting mood.

— Anatoly Kudryavitsky