In addition to the major categories of words above, there are also three important minor categories, PREPOSITIONS, DETERMINERS and CONJUNCTIONS.
PREPOSITIONS are also uninflected forms. They form a closed class (as opposed to open set categories like nouns and verbs) insofar as the number of them is finite (i.e. new prepositions are very infrequently added to English). The class consists of items such as to, by, with for, at, on, in, out, over, up, down, under, beneath beside, above, below and so on.
*Prepositions occur with Noun Phrases (to John, on the table, at home, in the afternoon) in which case the phrases are usually called Prepositional Phrases.
*Some prepositions specifically mark functional roles such as agency by (they were tracked by dogs), instrument with (they ate their peas with knives), recipient (I sent it to Mom), beneficiary (I made it for you) and so on.
*Other prepositions indicate spatial relations or direction (The book is on the top shelf, Mary climbed up the ladder to get it).
*They can also occur alone as, for instance the sole realisation of a Goal: location (John went out) or a locative predicate (Mary is in).
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