Applying several names to an entity (polynomy) reflects the ability to categorize entities in different ways. Two experiments demonstrate preschoolers' abilities to apply multiple labels to representational objects and to people. In Experiment 1, 3-and 4-year-olds labeled representational objects and verified labels for story characters. In both tasks children reliably produced or accepted several words per entity and accepted a high percentage of both class-inclusive and overlapping word pairs. These results were replicated in Experiment 2; 3-to 5-year-olds also completed appearance-reality and receptive vocabulary tests. The mean number of words produced in the labeling task was significantly related to receptive vocabulary, but not to appearance-reality performance. The results indicate that preschoolers represent an entity as belonging to multiple categories (e.g., dinosaur and crayon). Implications for cognitive and language development, particularly the appearance-reality distinctic/n and the mutual exclusivity bias, are discussed.The objects and organisms that inhabit our environment are complex and multifaceted, with many aspects and attributes. Any entity belongs to many different categories defined by particular aspects and attributes. Adults can conceptualize these categories and represent them by using a variety of words (i.e., category labels). For example, an organism may be labeled kitten, cat, feline, carnivore, mammal animal and pet. Some words highlight specific attributes; for example, kitten specifies an age-restricted category. Many words differ in inclusiveness; for example, cat is subordinate to animal. Such words form class-inclusion hierarchies. Other words form a cross-classification matrix in which the denoted categories overlap but are not inclusive (e.g., cat and pet). The ability to produce multiple words for an entity, denoting multiple categories with various semantic relations (i.e., inclusion; overlap), is referred to as polynomy, l