This book attempts to provide an inventory of uses of prepositions.这本书试图对介词的用法作一总结。I didn't understand what the teacher said about prepositions, because she only skated over it.我不明白老师所讲的关于介词的内容，因为她只是一带而过讲了一下。He tells her not to end her sentences with prepositions.他告诉她句尾不要用介词。