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.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use astounded + to-infinitive for the directly documented infinitival construction; use astounded at/by + noun phrase for the separately documented prepositional construction.
Decision table for Be Astounded To Do vs. Astounded By Something
Meaning / situation
Construction
Decision
reaction followed by an event
astounded + to-infinitive
use the documented infinitive complement
cause/source of reaction
astounded by/at + noun phrase
use a documented prepositional complement
Quick tests
Reaction-source test
Are you presenting the event with an infinitive, or naming the cause/source of the reaction?
If yes: Use “astounded to + verb” for the infinitive construction.
If no: Use “astounded by/at + noun phrase” when naming the cause or object.
Caveat: The reviewed evidence supports these complement patterns without making them mechanically interchangeable.
Examples
Example
She was astounded to hear the announcement.
The infinitive presents the event that prompts the reaction.
Example
They were astounded by the response.
“By” introduces the source of the reaction.
Example
He was astounded at the size of the queue.
“At” can introduce the object of astonishment in the documented pattern.
Further guidance
Core difference
Use astounded + to-infinitive for the directly documented infinitival construction; use astounded at/by + 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 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.
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 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.
