Be Afraid To Do vs. Afraid Of Something distinguishes two directly documented complement patterns for the adjective “afraid.” Use afraid + to-infinitive for the directly documented infinitival construction; use afraid of + noun phrase for the separately documented prepositional construction. The page stays within those attested patterns and does not infer a broader rule from synonymy.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use afraid + to-infinitive when the adjective takes its documented infinitive complement; use afraid of + noun phrase when the complement is introduced by the documented preposition.
Key details
Confusion Familyadjective-complement
Rule Familyadjective complementation
Termsafraid + to-infinitive, afraid of + noun phrase
Choose the right form
Decision table for Be Afraid To Do vs. Afraid Of Something
Complement
Pattern
Use
action/event expressed by infinitive
afraid + to-infinitive
afraid to ask
object/situation introduced by preposition
afraid of + noun/-ing
afraid of heights; afraid of falling
Quick tests
Complement-shape test
Is the complement an action expressed as an infinitive, or an object/situation introduced by “of”?
If yes: Use “afraid to + verb” for the documented infinitive pattern.
If no: Use “afraid of + noun/-ing” when the feared thing/situation is introduced by “of.”
Caveat: The two patterns overlap in broad fear meaning but are not mechanically interchangeable in every sentence.
Examples
Example
She was afraid to ask the question.
The action is expressed with the documented to-infinitive complement.
Example
She was afraid of the noise.
A noun phrase follows the documented preposition “of.”
Example
He is afraid of failing the test.
An -ing form can function after “of” as the feared activity/situation.
Further guidance
Core difference
Use afraid + to-infinitive for the directly documented infinitival construction; use afraid of + noun phrase for the separately documented prepositional construction.
Style Boundary
Treat this as a comparison of directly documented complement patterns, not as a claim that every other complement is impossible. Choose the construction that matches the intended grammatical relationship.
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.
Be Alarmed To Do vs. Alarmed At Something distinguishes two directly documented complement patterns for the adjective “alarmed.” Use alarmed + to-infinitive for the directly documented infinitival construction; use alarmed at + noun phrase for the separately documented prepositional construction. The page stays within those attested patterns and does not infer a broader rule from synonymy.
Be Amused To Do vs. Amused By Something distinguishes two directly documented complement patterns for the adjective “amused.” Use amused + to-infinitive for the directly documented infinitival construction; use amused by + noun phrase for the separately documented prepositional construction. The guide stays within those attested patterns and does not infer a broader rule from synonymy.
Be Annoyed To Do vs. Annoyed About Something distinguishes two directly documented complement patterns for the adjective “annoyed.” Use annoyed + to-infinitive for the directly documented infinitival construction; use annoyed about + noun phrase for the separately documented prepositional construction. The page stays within those attested patterns and does not infer a broader rule from synonymy.
Be Astonished To Do vs. Astonished At Something distinguishes two directly documented complement patterns for the adjective “astonished.” Use astonished + to-infinitive for the directly documented infinitival construction; use astonished at + noun phrase for the separately documented prepositional construction. The page stays within those attested patterns and does not infer a broader rule from synonymy.
Be Astounded To Do vs. Astounded By Something distinguishes two directly documented complement patterns for the adjective “astounded.” Use astounded + to-infinitive for the directly documented infinitival construction; use astounded at/by + noun phrase for the separately documented prepositional construction. The guide stays within those attested patterns and does not infer a broader rule from synonymy.
Be Concerned To Do vs. Concerned About Something distinguishes two directly documented complement patterns for the adjective “concerned.” Use concerned + to-infinitive for the directly documented infinitival construction; use concerned about + noun phrase for the separately documented prepositional construction. The page stays within those attested patterns and does not infer a broader rule from synonymy.
