What components can prepositional phrases serve as?

Preposition phrases can be used as predicative, adverbial, attributive and complement in sentences.

Preposition phrases cannot be used alone, and a single preposition does not act as any sentence component. Preposition phrases must be used together with nouns, pronouns and gerunds, and act as predicative, attributive, object complement and adverbial in sentences.

Preposition phrases can be used as predicative.

Mr. Smith is still sleeping. Mr. Smith is still sleeping.

Preposition phrases can be used as adverbials.

The children are playing by the river. The children are playing by the river.

Preposition phrases can be used as attributes.

The woman in the room is his wife. The woman in the room is his wife.

Preposition phrases can be used as object complements.

We found her in tears. We found her crying.