In children’s literature, genre identifies books according to content. Beginning at the left of the genre tree, we see that all literature is either prose or poetry. To define poetry, the initial impulse might be to identify it as rhyming, or condensed, or rhythmic. Yet these obvious elements of poetry are not true distinctions. Some poetry does not rhyme. Some poetry is longer than some prose. Some poetry is less rhythmic than some prose. With all the forms poetry can take—haiku, sonnet, couplet, blank verse, limerick, narrative, cinquain, and free verse, to name a few—finding a definition that both identifies them all and distinguishes them from prose is next to impossible. It is easier and more practical to define poetry by saying what it is not. The most obvious “not” is that poetry is not written in paragraphs.

Poetry may appear on the page as a single line, a thin column, or in the shape of a tree, but not in a paragraph. Prose, on the other hand, is always written in paragraphs. Beyond that difference in format, the function of the two literary forms is identical: Both poetry and prose thoughtfully explore the world, give insight into the human condition and experience, and bring pleasure to the reader.

The difference between fiction and nonfiction is verifiability. Fiction springs largely from the author’s imagination. An idea, question, or incident from the real world may give rise to a work of fiction, and the setting and even many details may be verifiable, but the plot comes from the workings of the mind. In Staple’s (2005) Under the Persimmon Tree, the setting and story involve the actual events in and cultural trappings of Afghanistan in the days after the attack on the World Trade Center in New York City, including the American counterstrike, the Taliban’s repression of women, and the careful descriptions of Afghani cities and villages. However, the plot revolves around two fictional characters who eventually meet in a refugee camp. If this book were nonfiction, however, it would be wholly factual—no fictional elements. All the evidence and facts presented in nonfiction books can be verified. The distinction between fiction and nonfiction is similar to determining which answer is correct on a true-false test: If any part of the statement is false, the answer is false. If any part of the book is fiction, the whole book is categorized as fiction.

Nonfiction books are classified as biography and informational. Biography (and autobiography) tells the story, or at least part of the story, of an actual person’s life. As with all nonfiction, reliable sources and documentation are imperative.

Informational books are called nonfiction in adult publishing. Children’s libraries classify all books in one of ten categories (ranging by 100s from 000 to 900) in the Dewey Decimal System. All except the 800s (literature—fiction and poetry) are informational books. Anything in the world is grist for the nonfiction mill: building a violin, life in China, the history of the ball bearing, animals that hibernate, how governments work, and so on. In the last 25 years, no area of children’s literature has changed so dramatically. Although some excellent informational books were written decades ago, in recent times subject matter has broadened, the quality of writing and illustration has improved, and the number of books published has increased.

Realistic fiction and fantastic fiction have much in common. Both are invented stories, often with invented characters, and they may take place in invented settings. Even when the setting is real, such as Boston or Berlin, the exact neighborhood is often imagined. The difference between realism and fantasy lies in the laws of our universe. If an invented story takes place in the world exactly as we know it—where dogs bark, trees are green, and gravity is everywhere—it is realistic fiction. If a story has one or more elements not found in our world—if animals speak, magic is present, or time travel is involved—it is called fantasy. The rest of the story might be absolutely realistic, but it is called fantasy if it contains any deviation from natural physical law.

The aim of both contemporary realistic fiction and historical fiction is to tell an interesting story about people in our world. The definitions are clear in the names of the genres. Contemporary identifies a story that takes place in today’s world; historical indicates a tale that happened earlier, as in pioneer America or medieval England. At times, though, the difference between the two genres depends on the age of the reader. Some people classify a story that happened during the collapse of the communist government in Eastern Europe as contemporary; to others, it is clearly historical.

Like historical and contemporary fiction, the division between traditional fantasy and modern fantasy relates to antiquity. Some stories are as old as humanity. These ancient stories are called traditional because they are part of our human tradition. Their origin is oral; their authors are unknown. Although they are now preserved in print, those who first wrote them down, such as the Brothers Grimm, were not authors, but collectors. If a fantasy story has an identifiable author, and therefore originated in print, it is called modern fantasy. Thus, the tales of Hans Christian Andersen are classified as modern fantasy because we know he created them, even though the tales read like traditional stories.

Science fiction, included under the modern fantasy heading, deals with scientific possibilities. Both modern fantasy and science fiction contain story elements not found in the known universe, such as being able to change shapes or read another character’s thoughts. In fantasy, those abilities just are or come about by magic—no questions asked. In science fiction, they result from an injection of distilled fluids discovered in the mucous membranes of a poisonous tree frog or from altering a person’s brain chemistry using microlaser bursts. The otherworldly elements in science fiction are based on extrapolated scientific fact pushed into logical but unproven possibilities, such as creating a bionic being that is a perfect reproduction of an existing woman. Modern fantasy needs no such justifications: The character’s double appears by magic.

While knowing the different genres can offer understanding in the field of children’s literature, none of the definitions is watertight. The categories are not to be slavishly followed. It is possible to make a solid case that some books belong in more than one genre. For example, Livia Bitton-Jackson’s I Have Lived a Thousand Years: Growing Up in the Holocaust (1997), a compelling tale of young Livia and her Jewish family being taken from their native Hungary to Auschwitz during World War II, can be classified as both biography and historical fiction. Ruth Heller’s series of informational books about the parts of speech, including Mine, All Mine: A Book About Pronouns (1997) and Fantastic! Wow! And Unreal!: A Book About Interjections (1998), are, at the same time, also books of poetry. The correct category for some titles depends not on immutable definition, but on personal decision.

Although genre lines at times may blur, these designations are used most often by adults to organize the field of children’s literature. These categories are less important to children, however. Young readers usually do not care if a book belongs to a certain genre. What they want is a good book, regardless of the classification. But adults can use the six genres to help understand the field of children’s literature more clearly, to draw on a framework for discussing books, and to provide a yardstick for determining what holes exist in their own particular reading backgrounds. If a teacher has never read modern fantasy or science fiction, for instance, that becomes immediately apparent when considering each of the genres. A self-check of our reading backgrounds can help us realize where we need more exposure, can provide direction to broaden our personal reading, and ultimately can help us serve students better. However used, the genres of children’s literature provide a road map for those interested in finding their way about.

Picture book and poetry are two formats also important in children’s literature. These two formats are so closely associated with categorizing books for children they have become pseudo-genres.  The picture book, still a mainstay of beginning reading and the primary-grade classroom, has extended its appeal to include older children and also to offer expanded information in nonfiction picture books.  Poetry, like prose, includes all the genres of literature. However, we choose to treat poetry as a separate genre because too few poems are available to study them under the same classifications we use for prose. If we were absolutely accurate, we would study “biographical prose” and also “biographical poetry,” “modern fantasy prose” as well as “modern fantasy poetry,” and so on. Because of the relatively small number of published poems, we look at poetry as a whole and at the various forms of poetry instead of concentrating on the content.