Children grasp almost 20,000 words by the age of six, and their sentences are larger and more complex. But what amazes me the most are the fresh intricacies in their mental processes—their wheels are continuously turning. Even young children make connections between items they learn about. They ask questions about things they don't understand, and they make assumptions about how the world works based on what they know. Around age seven, kids start to lose words that they've learned since they were little kids. By age nine, they usually know which words they're going to lose. By the time they're 11 or 12, they can only speak about half as many words as adults can read. The brain is more efficient at learning new words when you're young rather than old because there's so much room for growth. As you get older, parts of your brain associated with language learning stop growing and replace them with other parts of the brain, so you need more new vocabulary to keep up. The number of words a child knows increases until around age 10 when it starts to drop again. This is called the word gap. Kids close this gap by learning new words and using existing words in different ways. For example, one kid may have trouble saying "ball" but will know what kind of ball it is if you show him or her several pictures of different kinds of balls.