Cambridge directly records certain + to-infinitive and certain of + noun, allowing the two attested structures to be compared without claiming they are freely interchangeable.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “certain to do/be…” for something expected or sure to happen. Use “certain of something” when certainty is about a fact, result, or object of belief.
Key details
Confusion Familyverb-complement
Rule Familyverb-complementation
Termscertain to do, certain of something
Further guidance
Core difference
Cambridge documents certain + to-infinitive and certain of + noun as standard patterns with different complement roles.
Style Boundary
Use the construction that matches the intended grammar: infinitive after certain for the expected action/state, and of before the object or fact of certainty.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
Certain↗ (opens in a new tab)Cambridge University Press · Direct learner-dictionary evidence for certain of + noun and certain + to-infinitive.
Cambridge directly records amazed + to-infinitive and amazed at + complement, making it an evidence-safe replacement for the unsupported Satisfied proposal.
Oxford directly records both ashamed + to-infinitive and ashamed of + noun/pronoun. The guide compares those attested structures without inventing an unsupported parallel complement.
Oxford directly documents averse to (doing) something. This is a prepositional to + noun/-ing construction, so a bare infinitive should not be assumed to be an interchangeable complement.
Oxford documents the idiomatic adjective pattern bent on (doing) something for determination. The evidence does not license a parallel bent + to-infinitive complement for that same meaning.
