Can English preposition phrases be used as definite sentences

No. It can only be an adverbial or an epithet.

It is a fish called a whale shark.

The whale shark is a shark that can reach up to 20 meters in length and is the largest fish in the world, a species of fish called the whale shark.

The whale shark is a shark that can reach up to 20 meters in length and is the largest fish in the world, a species of fish called the whale shark.

The whale shark is a shark that can reach up to 20 meters in length and is the largest fish in the world.

When a relative pronoun is used as a prepositional object in a definite clause, the preposition can be placed either at the beginning of the clause or at the end of the clause. However, it is more formal to place it at the beginning of the clause. Such as:

this is the book for which you asked.This is the book you want. (The relative pronoun is used as the object of the preposition for, and the preposition for is placed at the beginning of the clause, i.e., before which).

this is the book which you asked for.This is the book you want. (The preposition for is placed at the end of the clause, which can be omitted here).

If the preposition and the verb or adjective form a fixed phrase, the preposition should not be advanced, as if:

the old woman whom he is taking care of is my grandmother.The old man he was taking care of was my grandmother.

When the relative pronouns who and that are used as prepositional objects, the prepositions must be placed at the end of the sentence. Such as:

the people who you were talking to are swedes.The people you talk to are Swedes. (When the relative pronoun nominative who is used as the object of the preposition to, the preposition to must be placed at the end of the clause, and can be omitted in the colloquial language of who).

here is the car that i told you about.This is the car I talked to you about. (The relative pronoun that is used as the object of the preposition about, and the preposition about must be placed at the end of the clause).

Sometimes the clause has other components, and the preposition is placed in the clause. Such as:

this is the boy whom he worked with in the office.That's the boy he worked with.

It doesn't seem to be, as long as it is a phrase composed of a verb and a preposition, and the relative pronoun is who or which, it can be advanced in advance.

Verb-centric phrases.

Common ones include verbs plus prepositions, verbs plus adverbs, etc.

For example: come

across,go

through

Prepositions are paired with other pronouns or nouns to form prepositional phrases.

1.Preposition: Also known as a preposition, it is generally placed before a noun, pronoun, or word equivalent to a noun. Generally, it is not stressed, and it is not a separate sentence component, but only indicates its relationship with the following words to other sentence components. Prepositions can be divided into 5 categories:

1) Simple prepositions, such as about, for, from, to, on,..

2) Compound prepositions, such as into, outside, upon, without, ,..

3) Double prepositions, such as from

behind,until

after,from

among,..

4) Participle prepositions, such as regarding, including, concerning,..

5) Phrase prepositions, such as along

with,on

behalf

of,owing

to,inspite

of,onaccount

of,..Then look at the definition of a prepositional phrase: a preposition is formed together with a noun or a word equivalent to a noun (prepositional object) after it, and is mainly used as an adverbial, a definite, a predicate in a sentence, and sometimes a compound object. For example: among

youngpeople,in

english,in

hisearly

thirties,in

arage.

Based on these, what really needs to be paid attention to should be the "phrase preposition", not the "preposition phrase" by definition