During their third year, children begin using pronouns and plurals in their speech and understand the concept of “mine.” They also begin using language to describe ideas and information and to express physical or emotional needs and desires.
Shelov, S. P. (Editor-in-Chief). (2004). Caring for Your Baby and Young Child: Birth to Age 5. The American Association of Pediatrics. Revised edition. New York: Bantam Books.