Differentiate between preposition and adverb.

Is the following explanation enough to find out the difference between a preposition and adverb used in a phrasal verb.. If not, then please can you give another alternative.

Many of the words in the preposition list can also be used as adverbs. The problem for you is to figure out when a word from the list is being used as an adverb or as a preposition. When in doubt, ask the questions whom or what after the word. If there is a noun or a pronoun to answer the question, then the word is a preposition with an object--a prepositional phrase. If there is not a noun or pronoun to answer whom or what, then the word you are worried about is an adverb.

Example: The girl looked over and then ran down the street.

Both the words "over" and "down" are on the preposition list. Say the word "over" and add "over what?" There is no what or whom word after "over." Now say "down what?" -- "down the street." There is a noun "street" which tells what after the word "down." Therefore, "down" must be a preposition with the prepositional phrase being "down the street."


These rules work for all those sentences that contains a preposition. See the following sentence;

Here (in the 1st sentence) on is a preposition and answers the question what.
1. I hadn't reckoned on being the center of attention. ( on what? on being the center of attention.)
We abided by the rules.
He accounted for the discrepancy.
They asked for an extension.
We are banking on good weather tomorrow.
Please bear with the delay.


But they doesn't work for this one;

Here on is not a preposition but an adverb and still answers the question what.
2. He kept on changing the subject. (on what? on changing the subject.)

GB