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Prepositions with nouns

Of proof or as proof?

Use as proof when something serves as evidence. Of proof is correct only in certain noun phrases such as burden of proof.

Quick answer

Which expression is correct?

As proof means as evidence or confirmation. Of proof is not a general replacement for this expression, but it appears naturally in established phrases like burden of proof or piece of proof.

She showed the receipt as proof of payment.
The law defines the burden of proof in court.
He submitted photos as proof of ownership.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
as proof of + fact

Showing evidence or confirmation

Use as proof when something functions as evidence.

They used the email as proof of agreement.
She presented her ID as proof of age.
2
proof of + noun

Naming the thing that is proven

Proof of is a common noun phrase meaning evidence for something.

We need proof of identity.
There is no proof of fraud.
3
burden of proof

Talking about legal responsibility

Of proof appears in several fixed legal and formal expressions.

The prosecution carries the burden of proof.
The contract changed the standard of proof.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
as proof
He showed the receipt as proof.
Something serves as evidence.
of proof
The burden of proof is on the claimant.
Part of a larger noun phrase, not a general substitute for as proof.
proof of
They demanded proof of address.
Evidence related to a specific fact or condition.

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using of proof instead of as proof

Use as proof when introducing evidence.

✕ She showed the photo of proof. ✓ She showed the photo as proof.

Confusing proof of and as proof

Proof of names the thing proven, while as proof describes function.

✕ He used the receipt proof of payment. ✓ He used the receipt as proof of payment.

Quick practice

Choose the expression that matches the intended meaning.

1. She used the contract ___ proof of ownership.
2. We need proof ___ address.
3. The judge explained the burden ___ proof.

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Frequently asked questions

Is as proof always followed by of?

Often, but not always. The context may already make the meaning clear.

Can of proof stand alone?

Usually no. It normally appears in a larger phrase such as burden of proof.

What is the difference between proof of and as proof?

Proof of names evidence for something, while as proof describes how something is being used.

of, about, against, to or for racism? of, about, for, in or on friendship? of, about, for, on or to thing? of, about, for, to or with sex? of, about, on, to or for moon? "of access" or "with access"? "of accommodation" or "for accommodation"? "of accuracy" or "for accuracy"? "of action" or "in action"? "of actor", "with actor" or "by actor"? "of address" or "to address"? "of administration" or "in administration"?

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