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English is not my native language. I read much more than I speak or hear. In fact, the only time I hear English being spoken is when I'm at my lectures in college or watching a movie.
However, I read a lot, and I know how to words are spelt but don't know how they are enunciated.
For example, I have long know the word "lingerie", having come across it in my reading, but only recently knew that it was pronounced "lawngzere" and not "lingerie".
So how do I know how a word in pronounced just by looking at it's letters on a page?