A recent study by researchers from Penn State, UC-Irvine, and Columbia University have confirmed important early literacy information. The jargony abstract says: "Even after extensive covariate adjustment, 24-month-old children with larger oral vocabularies displayed greater reading and mathematics achievement, increased behavioral self-regulation, and fewer externalizing and internalizing problem behaviors at kindergarten entry." What that means is that the children with higher oral vocabularies at age two have an easier time succeeding academically and behaviorally at school when they get there.
The best and easiest way to enrich vocabulary is by reading picture books. No, really! Children's books are lousy with rare words, or rich vocabulary words. Children's books have 50 percent more rare words in them than does adult prime-time television and the conversation of college graduates (read more here)! When you read out loud to your child, and accompany the words you're reading with pictures, the children have a context to place the word in and it's an authentic way for you to connect with your child, as opposed to just trying to use flash cards or insert Brobdingnagian words into your conversation. See what I did there?