A prepositional phrase is a group of words that begins with a preposition. Examples are: at a loss, in the corner, by the way and on the roof. A prepositional phrase may end with a noun, pronoun, gerund or clause which acts as the object of the preposition.
For example, in the prepositional phrase at home, the noun home acts as the object of the preposition at. In the phrase from Rahul, the noun Rahul acts as the object of the preposition from.
The noun which acts as the object of the preposition may be modified by an adjective or another determiner. Consider the prepositional phrase given below.
From your dearest son
Here the object son is modified by the adjective dearest and the possessive determiner your.
Function of a prepositional phrase
Although a prepositional phrase begins with a preposition, it does not serve the same purpose as a preposition.
Prepositional phrases usually function as adjectives or adverbs.
When a prepositional phrase is used as an adjective, it answers the question ‘Which one?’
The students in my class ask numerous questions.
Which students? The ones in my class
The letter from Maya confessed that she had lied about her affair with Ravi.
Which letter? The one from Maya
The apples on the tree are ripe.
Which apples? The ones on the tree
When used as an adverb, the prepositional phrase answers questions such as ‘How?’, ‘When?’ or ‘Where?’
The children were playing in the garden.
Where were the children playing? In the garden
His father died in 1995.
When did his father die? In 1995
She put the books on the table.
Where did she put the books? On the table
He fought with all his might.
How did he fight? With all his might
The students learned the poem by heart.
How did they learn the poem? By heart
Note that a prepositional phrase cannot function as the subject of a sentence.