A big vocabulary is like a full toolbox; you might not need every tool for every job, but every tool has a time and place. The way we pick up new vocabulary is a fascinating and complicated field, but measuring our vocabulary can be equally complicated. Researchers trying to learn more about this field have created testyourvocab.com. The test has you go through and choose the words you can define and then estimates your vocabulary at the end. A typical score for a native English speaker is between 20,000-35,000 words. Keep in mind, there is most probably a sample bias at work here, since the people most likely to test their vocabulary are the same people who would value a large one. Nonetheless, it’s an interesting experiment. You might be surprised by how much you know.