Children's early noun vocabularies are dominated by names for shape-based categories. However, along with shape, material and colour are also important features of many early categories. In the current study, we investigate how the number of shared features among objects influences children's novel noun generalizations, explanations for these generalizations and spontaneous speech. Preschool children and adults were presented with test objects that shared only one feature (e.g. shape) or that shared two features (e.g. material and colour). After each trial, participants were asked, "how did you know that was your [novel name]?" Overall, participants generalized novel names on the basis of shape more when objects shared shape and a second feature with the exemplar. All participants provided shape-based explanations of their choices, but explanations were increasingly more abstract across development. Finally, children's spontaneous speech was dominated by references to the objects' shape, and this did not change across development or number of shared features. Overall, these data demonstrate that the shape bias is enhanced when objects share shape and a second feature but weakened for 3-year-old children when objects share two non-shape features. These findings have implications for our understanding of how children learn names for objects that belong to multiple categories.