The word is probably a preposition if it is followed by a noun or a noun equivalent. Of course, this can be misleading because verbs are also followed by noun objects. That said, identifying prepositions is not all that difficult. There are only a limited number of prepositions in English so if you want you can even memorize their list.
Here is a list of the most common prepositions in English.
- I went to the market.
- She is above average in intelligence.
- The cat is on the roof.
- The farmer killed the dog with his gun.
- She was standing behind the door.
- He walked towards the door.
- The bride walked into the hall.
- I work from nine to five.
Prepositions are very important words and they are absolutely necessary to establish the connection between a particular noun and another word in a sentence.
Consider the sentence given below.
- The lion is in the cage.
What will happen if we remove that preposition in from the sentence?
- The lion is the cage.
As you can see this sentence doesn’t make much sense.
Adverbs, on the other hand, are mainly complementary. Even if you remove them, the sentence will still make good sense. Of course, some meaning will be lost, but there will be no ungrammaticality.
Consider the two sentences given below. They both mean the same, but the second sentence provides some extra information, thanks to the presence of the adverb well.
- She speaks English.
- She speaks English well.