This paper reports on partial knowledge in two-year-old children's learning of the regular English plural. In Experiments 1 and 2, children were presented with one kind and its label and then were either presented with two of that same kind (A[right arrow]AA) or the initial picture next to a very different thing (A[right arrow]AB). The children in A[right arrow]AA rarely produced the plural. The children in A[right arrow]AB supplied the singular form of A but children in A[right arrow]AA did not. Experiment 3 compared the performance of English-speaking and Japanese-speaking children in A[right arrow]AA with common and novel nouns. The Japanese-speaking children (learning a language without a mandatory plural) supplied the singular form of A but the English-speaking children did not. The findings indicate young children learning English know there is a plural to be learned before they have fully worked out the rules of production or acquired the necessary singular-plural pairs for broad generalization.