There is a big difference between learning a word and remembering a word. You can know the meaning of a word but not be able to remember how to say it. Everyone has done this. You can also know how to use a word but not what the definition of it is.
There are many levels of word learning. When most people think of learning a word they mean remembering how to say the word.
If you want to learn Mandarin Chinese, Spanish or Thai to sign up with the World Word Exchange and start learning now.