Like Romanticism, Realism is both a recurring style in literature and the name for a particular period of American literature in the late 1800s-early 1900s when writers intentionally developed this style in reaction against Romanticism.
Oxford English Dictionary, 3a. Inclination or attachment to what is real; (hence) the attitude or practice of accepting a situation as it is and being prepared to deal with it accordingly; any view or system contrasted with idealism
4. Esp. in reference to art, film, and literature: close resemblance to what is real; fidelity [faithfulness, accuracy] of representation [mimesis], rendering the precise details of the real thing or scene. Also: an instance or example of this. [compare verisimilitude]
Realism as style . . .
Attention to detail (verisimilitude)
Descriptions based on knowledge or experience (in contrast to imagination, which inspires Romanticism)
Characters motivated by real-life urges like greed, lust, confusion more than honor, chivalry, service, etc.
Characters are more complex mixes of good and bad compared to popular or extreme romance narratives, where characters are more symbolic types, like gallant heroes, dastardly villains, innocent and helpless women, faithful servants.
Greater attention to detail (verisimilitude) may create a more detailed setting with potential distractions from simple narrative.
The many conflicts and complications inherent in everyday reality
Realistic fiction or writing may devote more description to work or labor compared to Romanticism, which does not typically represent toil or everyday labor, and elevates conflicts to issues of honor, heart, dignity, responsibility, or heroism rather than to the everyday encounter and resolution of technical or material difficulties.
Speech in realism is more vernacular and idiomatic, like common people of particular classes or regions talk. Romantic rhetoric often strains to be more elevated or universal and tends to extremes of intimacy or excess.
Presence of humor, whose "deflating" tendencies find a natural fit with Realism's attention to everyday reality or limits, which humans endure by laughing them off. In contrast, Romanticism generally takes itself seriously; its dreams are easily punctured by wit and humor. (e.g. Mark Twain, "Fenimore Cooper's Literary Offenses")
Realism as attitude . . .
Romanticism as anything but the here and now
Realism = here and now; "get used to it"; "it is what it is"
Social / Political Appeals of Romanticism & Realism . . .
Romanticism loses credibility by being unrealistic but wins imaginatively by being able to think outside the box, imagine better (or worse, or alternative) possibilities.
Realism deals more directly with everyday realities but in the process accepts their limits on imagination or possibility.
(On the other hand, the surprising nature of reality may contrast with the formulaic nature of romance or legend: "Truth is stranger than fiction." When people make up stories, their stories usually fall into familiar or predictable patterns that assume individual autonomy and self-determination. Historical reality, however, is more like weather systems—determined by multiple factors and taking unpredictable forms. On another scale of measure, Romantic fiction tends to operate in a comparatively small world with a limited number of characters; reality is infinite in scale and ranges from the microscopic to the cosmic in entity and effect: "I am the master of my fate" vs. "the Butterfly Effect.")
Specific literary & historical comparisons of Romanticism & Realism
Verisimilitude is a literary term describing the surface quality of realistic literature: -"the appearance of being true or real; likeness or resemblance to truth, reality, or fact; probability."
Realistic style may be marked by the prominence of particular tropes or figures of speech. Roman Jakobson's Structuralist study of Metaphor & Metonymy from Fundamentals of Language (1956) remains influential in formal studies of Realistic literature. According to Jakobson, Romantic-poetic style emphasizes metaphor as its most characteristic figure of speech, while Realistic-prosaic style emphasizes metonym.
Realism as period . . .
Approximate dates of American Realism: 1865-1910.
Like Romanticism, however, Realistic styles and values appear both earlier and later.
In study of American Literature by periods, Realism begins after the Civil War (1861-65), succeeding Romanticism (1820s-60s) and continues until the 1910s or World War 1 (1914-18), when it is succeeded by Modernism. Realism continues in more symbolic styles in the Modernist writings of Ernest Hemingway, F. Scott Fitzgerald, and William Faulkner, among others.
Historically, American Realism often appears as
Realism's attention to socio-economic class may reflect the Gilded Age when, as in contemporary America, increasing concentrations of wealth replaced the "common-man" politics of the Romantic era.
A recent-history parallel to Romanticism > Realism may be the 1960s > 1980s (etc.)
1960s: growth of government support for education, war on poverty > growth of middle class, Civil Rights Movement, Women's Liberation, anti-war movement, other campaigns and legislation for human rights;
1980s: Conservative reaction, Reaganomics (Neoliberalism), increasing inequality between stockholders and workers; Angry White Men, property & corporate rights over human rights
Major authors & texts of American and European Realism
major American authors: William Dean Howells (1837-1920), Henry James (1843-1916), Mark Twain (1835-1910), Edith Wharton (1862-1937)
European antecedents and contemporaries: Gustave Flaubert (France, 1821-80) (Madame Bovary, 1857); Honore de Balzac (France, 1799-1850) (La Comedie humaine, 1842-48); Leo Tolstoy (Russia, War and Peace)
later American writers in tradition: Scott Fitzgerald (1896-1940), Louis Auchincloss (1917-2010), Kay Boyle (1902-92)
stylistic tendencies: verisimilitude; urban settings; meetings of differing classes or of Americans with Europeans ("the international theme"); accuracy of speech patterns; accuracy in human motivation; "social problem novel"
romantic survivals: romantic fantasies tend to be internalized, within characters' consciousness.
major American authors: Harriet Beecher Stowe (1811-1896), Sarah Orne Jewett (1849-1909), Mary E. Wilkins Freeman (1852-1930), Kate Chopin (1851-1904), Bret Harte (1836-1902), George Washington Cable (1844-1925), Charles C. Chesnutt (1858-1932), Willa Cather (1873-1947)
European antecedents: possibly Ivan Turgenev (Russia and France, 1818-83) (The Hunting Sketches, 1847-1851), but, as a "local" tradition, the movement's influences are open to question.
later writers in this tradition: Zona Gale (1874-1938), William Faulkner (1897-1962), Flannery O'Connor (1925-1964), Eudora Welty (1909-2001), Marjorie Rawlings (1896-1953), Katherine Anne Porter (1890-1980)
stylistic tendencies: short story or sketch is dominant genre; local dialects; legends or folk tales; stories often "framed" by an outside narrator who gives over to a dialect narrator
romantic survivals: rural landscapes; folk manners; kinship systems; sentimental characters; nostalgia
(Some sources add "veritism" to Realism's list of movements. This theory by Hamlin Garland [in Crumbling Idols (1894)] asserts a more scientific standpoint than Howells's moralism and emphasis on the "smiling" aspects of life but also opposes the "immoralism" of mainstream Naturalism derived from Zola. However, Garland's best work, such as the short story "Under the Lion's Paw," resembles naturalism, though perhaps less pessimistic and more reform-minded.)
major American authors: Theodore Dreiser (1871-1945) (Sister Carrie, 1900; The Financier, 1912; An American Tragedy, 1925); Stephen Crane (1871-1900) (Maggie, a Girl of the Streets, 1893; The Red Badge of Courage, 1895; "The Open Boat," "The Blue Hotel"), Frank Norris (1870-1902) (McTeague, 1899; The Octopus, 1901), Jack London (1876-1916) (The Sea Wolf, 1904; "The Law of Life"); Robert Herrick (1868-1938) (The Memoirs of an American Citizen, 1905; The Master of the Inn, 1908)
European antecedents and contemporaries: Emile Zola (France, 1840-1902), novelist (Nana 1880; Le Roman experimental, 1880); Hippolyte Taine (France, 1828-1893), philosopher and historian ("la race, le milieu, et le moment"); Thomas Hardy (England, 1840-1928) (Tess of the D'Urbervilles, 1891)
American antecedents: Rebecca Harding Davis (1831-1910) (Life in the Iron Mills, 1861); Herman Melville (1819-91)
later American writers in tradition: Faulkner (Old Man and others), Paul Louis Dunbar (1872-1906) (The Sport of the Gods, 1902), Sherwood Anderson (1876-1941) (Winesburg, Ohio, 1919; Poor White, 1920), James Farrell (1904- ) (Studs Lonigan, 1934), Ralph Ellison (1914- ) (Invisible Man, 1952), Richard Wright (1908-1960) (Native Son, 1940), John Steinbeck (1902-68) (The Grapes of Wrath, 1939)
stylistic tendencies: monotony, boredom, and violence of modern urban life; or, occasionally, primitive life on the frontier; interest in social relations evolving from Darwinian biology, social Darwinism ("survival of the fittest"), and plutocracy; concern with lower levels of society than Howells, Wharton, and James, plus effect of environment on these classes; viewpoint aims at detached, scientific objectivity regarding human subjects; psychological interests in deep-seated impulses of will or desire; environment or instincts determine human behavior; corresponding lack of human free will (compare Calvinism); tendency by author not to make moral judgments.
romantic survivals: extreme, exotic, or dramatic natural environments; semi-heroic individual struggling against a hostile or indifferent environment
Historical influences: Darwinian biology; laissez-faire capitalism; Calvinism (unknowable and random God in irrational cosmos); Taine's theory of "race, moment, and environment"; the Nietzschean "superman"