Many native speakers actually know little about their mother language.
Several weeks ago, when the writer was riding in a cab whose driver was a curious Pakistani man, she was asked to explain some words. Actually, the cab driver is keen on learning new English words by asking his passengers. However, though the writer was a native speaker, she racked her brain and struggled to explain the meanings by using some vague words and examples, which gave her a lesson that native speakers actually know little about their mother language. What’s more, she used some instances such as “Haste makes waste” in order to explain a proverb is nothing but a condensed saying that teaches a lesson. Finally, the writer only hoped the driver also owns a dictionary and works out the problem on his own rather than just listens to what native speakers say.
After all, it is obvious that it is one thing to use a word, but it is another thing to explain.