Abstract We investigated the roles of shape and function in object naming. Two-, three-, and five-year-olds and adults heard novel or familiar objects named; some participants also were instructed about the objects' functions. Then they were asked to generalize the names to new objects that preserved shape or functional capability; some participants also judged the objects' potential for carrying out the designated function. Children generalized the name by object shape regardless of instruction, but adults did so only in the absence of instruction or for familiar objects. Knowledge of function independent of naming became increasingly stronger and diverse over age. The strong developmental changes in the role of function bear on mechanisms of object naming.