One of the most important capacities which children employ when learning language is the capacity to generalize. A child who hears an utterance of a verbal expression while perceiving a particular object (or action, aspect, etc.) becomes normally able to apply the expression not only to this object but also to all those objects which, for him, are similar to the original one. These objects constitute his generalization class relative to the original object. Two kinds of generalization classes can be distinguished: species-determined, or innate, and species-indetermined, or acquired. Whereas children are born with the capacity to generalize in accordance with the former classes, they must undergo certain kinds of experiences in order to learn to generalize according to the latter classes. In the paper, it is shown that the capacity of children to generalize in accordance with both innate and acquired generalization classes plays a fundamental role in language acquisition. In particular, this capacity enables children to learn to associate a large number of words with the correct classes of objects and to acquire the creative ability of understanding and producing new sentences. (Author)