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Prepositions after verbs

Certify by, as, to, under or for?

Certify is commonly used with as and to. Other prepositions often belong to passive structures or legal and technical contexts.

Quick answer

How is certify used with prepositions?

Use certify as to identify a status or qualification. Use certify to when formally stating that something is true. By often appears in passive phrases such as certified by. Under can introduce a law or standard.

She was certified as a translator.
I certify to the accuracy of this report.
The product is certified by an independent agency.

Choose the pattern by meaning

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

1
certify as + role/status

Giving official status

Use certify as when someone or something receives an official classification.

The lab was certified as safe.
2
certify to + fact

Formally confirming something

Use certify to in formal or legal English to confirm a fact.

The witness certified to the document's authenticity.
3
certified by + authority

Naming the certifying authority

By introduces the person or organisation that gives certification.

The equipment was certified by the regulator.
4
certified under + rule/law

Certification within a system

Under can introduce a law, programme, or standard.

The product is certified under EU regulations.

See the difference in context

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

Construction
Example
Meaning
certify as
The course is certified as industry approved.
gives an official status or description
certify to
She certified to the truth of the statement.
formally confirms something
certify by
The documents were certified by a lawyer.
By introduces the authority in a passive structure
certify under
The company is certified under international standards.
Under introduces a legal or technical framework
certify for
The doctor certified him for travel.
Possible in limited contexts meaning approve for a purpose, but not the main general pattern

Common mistakes

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

Using certify by in active voice

By usually belongs to passive constructions.

✕ The agency certified by the product. ✓ The agency certified the product.

Confusing certify as and certify to

As gives a status; to confirms a fact.

✕ She certified as the report was accurate. ✓ She certified to the accuracy of the report.

Adding for unnecessarily

Certify often takes a direct object.

✕ The board certified for the software. ✓ The board certified the software.

Quick practice

Choose the expression that matches the intended meaning.

1. The engineer certified ___ the safety of the bridge.
2. The product was certified ___ organic.
3. The devices are certified ___ national standards.

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Frequently asked questions

What does certify to mean?

It means formally declare or confirm that something is true.

Can certify as be used for people?

Yes. For example: She was certified as a flight instructor.

Is certified by a fixed expression?

It is a common passive structure naming the certifying authority.

calculate, by, calculate, in, calculate, from "call for" or "call on"? "campaign for" or "campaign against"? cancel by, due, at, in or for? capitulate to, in, like, by or after? captivate by, for, with, from or in? "capture by" or "capture in"? "care about" or "care for"? carry with, by, in, to or into? carve into, out, in, on or with? cast in, into, for, by or on? "catch in", "catch by" or "catch on"?

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