four-o'clock, common name for members of the Nyctaginaceae, a family of plants found in warm climates, especially in the Americas, chiefly as herbs but often in the tropics as shrubs or trees. Species native to the United States are mostly restricted to the southern and Pacific regions, e.g., the sand verbena of the deserts. The four-o'clock, or marvel of Peru (genus Mirabilis), of tropical Asia and America and the woody bougainvillea vine with its showy bracts are widely cultivated as garden ornamentals in suitable climates and in greenhouses. Some members of the family are of minor importance medicinally. Four-o'clocks are classified in the division Magnoliophyta, class Magnoliopsida, order Caryophyllales, family Nyctaginaceae.