The number of the subject is marked in most third-person sentences both in the subject-noun (e.g., "dog/dogs") and in the verb (e.g., "barks/bark"). The verb inflection for number is redundant with the noun inflection except in those rare instances in which the subject-noun is not marked for number (e.g., "sheep/sheep"). Since the verb inflection for number is rarely crucial for determining the meaning of a sentence, and since number is marked in exactly the opposite manner in regularly formed verbs from the manner in which it is marked in regularly formed nouns, children might be expected to acquire the verb inflection for number relatively late in the course of language development. Sentences in which number was marked in (a) the verb only and (b) the subject-noun and the verb were presented to a sample of 24 children 4 years of age in both imitation and comprehension tests. The results indicated that the children did not comprehend the verb inflection for number even when the noun was unmarked, making the verb inflection the only cue for number. Despite explicit training on the meaning of unmarked nouns, the children understood the unmarked subject-noun as singular and responded to the entire sentence as if it were singular. At four years of age, the apparent number of the subject-noun is the primary cue for sentential singularity or plurality.