Prepositions are abstract words that have no concrete meaning. They merely show the relationships between groups
of words. A good way to test if a word is a preposition is to position it in front of phrases like "the box" or "the sides
of the box" and see if the phrase makes sense. For prepositions concerning time, try positioning the preposition in
front of a phrase like "the movie." (This rule works for about nine out of ten prepositions). Here are some