The sentence “I live in a forest” can be analyzed grammatically as follows:

Subject: “I”

This is the subject of the sentence, the person performing the action or being described.

Intransitive Verb: “live”

This is the main verb of the sentence. It is intransitive because it does not require a direct object to complete its meaning. The verb “live” simply describes the state or action of the subject.

Prepositional Phrase: “in a forest”

This phrase provides additional information about where the action of the verb takes place. It consists of:

Preposition: “in”

Object of the Preposition: “a forest” (which includes the article “a” and the noun “forest”).

Grammatical Structure:
The sentence follows the structure: Subject + Intransitive Verb + Prepositional Phrase.

The prepositional phrase “in a forest” functions as an adverbial phrase, modifying the verb “live” by specifying the location.

Is it one single function?
No, it is not one single function. The sentence is composed of distinct grammatical elements:

The subject (“I”) performs the action.

The intransitive verb (“live”) describes the action or state.

The prepositional phrase (“in a forest”) provides additional context (location) for the action.

Each part has its own role, but they work together to form a complete thought.