Try to learn what this preposition means by the context in which is used. You will notice that you have been doing this all along with most of the vocabulary introduced. It is a good way to learn a language because it is how children learn their native languages, by associating the sounds they hear with the context in which the sounds are uttererd. If the context changed continually, the children would never learn to speak. Also, the so-called meaning of a word is completely determined by the context in which it is spoken, so that in fact we cannot say a meaning is inescapably attached to a word, but that it shifts over time and from context to context.
[Lydia Davis, French Lessons I: Le Meurtre, da The collected Stories of Lydia Davis]