Literary forms are groups of literary works united by one or another formal and only formal properties (in contrast to literary genres , the selection of which is based on a combination of formal and substantial features). The border between forms and genres is permeable and historically variable: for example, a sonnet , in the early stages of its existence, gravitating towards genre nature (i.e., to a fairly defined range of themes and images), retained only some elements of the formal structure by the 20th century (14 poetic lines with a certain stanzaic pattern), while a monostich , originally characterized by a single formal attribute (single-line poem), in the works of Vladimir Vishnevsky acquires the properties of the author's genre . Disputes between proponents of formal and genre understanding of haiku accompany this kind of poetic miniature throughout the history of its existence in Western literary tradition.
By virtue of greater conventionality , the canonicalization of form in poetry, formal grouping is easier than in prose . At the same time, one can speak of literary forms in dramaturgy (for example, one-act plays as opposed to multi-act ones or monopieces in contrast to plays with a large number of actors). Literary forms should also include a phenomenon such as a palindrome (in those cases when we are talking about an author's work of art, and not about a separate palindromic word that exists in the language), since a palindromic text can be either poetic or prosaic.