Grammar – Can a sentence start with a relative clause?

grammarrelative-clauses

I'm currently preparing for GMAT and I stumbled across a sentence

That a ruined structure found at Aqaba, Jordan, was probably a church
is indicated by its eastward orientation and overall plan, as well as
by the artifacts, such as glass oil-lamp fragments, found at the site.

I'm able to figure out the meaning of the sentence but I'm not able to figure out the structure because as per GMAT official guide, the sentence is correct. Can someone please explain the structure of this sentence.

Best Answer

That's not a relative (adjective) clause; it's a that-clause—a noun clause (warning: grammar terms vary). It functions as a noun does in its various roles: subject, object, complement, appositive, etc.

This that is a conjunction, not a relative pronoun.
See Merriam-Webster at that conjunction

English and Language Usage's "resident" authority, linguist John Lawler explains:

There are two kinds of clauses in English that are introduced with "that". One kind is a noun clause (called a "complement"), which may appear (like a noun) as subject or direct object. These are tensed (finite) sentences with a "that" in front of them:

That you were shocked is perhaps not surprising.
I told him that you were shocked.

Source: (in a discussion of "clauses beginning with 'that'")

Your sentence (which I've simplified here for purposes of illustration) is in the passive voice:

That the structure was a church is indicated by its eastward orientation.

Let's put it in the active voice to better see what's happening:

Its eastward orientation indicates that the structure was a church.

That the structure was a church is your that-clause. In the active voice, it is the direct object of the verb indicate. Indicates what? That the structure was a church. As a direct object, it functions as a noun.

In the passive voice, the direct object is promoted to the subject position, replacing its eastward orientation. Now the that-clause is the grammatical subject, and again, it functions as a noun.

Further reading:

'That'-Clause

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