The Printable KISS Grammar Workbooks Back to KISS Level 2.2.2
Is it a Preposition?

If it looks like a duck,
and it quacks like a duck,
it's a duck.

     Many words that function as prepositions also have other functions. You find a prepositional phrase by asking the question "What?" after a word that can function as a preposition. When the word or words that answer that question form a sentence, the construction is not a prepositional phrase. 

(They are subordinate clauses, but you do not need to remember that now. 
Just remember not to put parentheses around them.)



Examples
Prepositional Phrase: We watched television {after dinner}.
Not 
a Prepositional Phrase:
We watched television after we had dinner.
Prepositional Phrase: {Before sunrise}, the birds begin to chirp.
Not 
a Prepositional Phrase:
Before the sun rises, the birds begin to chirp.
Prepositional Phrase: Billy can't swim {like her}.
Not 
a Prepositional Phrase:
Billy can't swim like she does.