Be Astonished To Do vs. Astonished At Something
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.
Use astonished + to-infinitive when the adjective takes its documented infinitive complement; use astonished at + noun phrase when the complement is introduced by the documented preposition.
Key details
Choose the right form
| Meaning / situation | Construction | Decision |
|---|---|---|
| reaction expressed with an infinitive | astonished + to-infinitive | use the documented infinitive pattern |
| reaction to a named thing/result | astonished at + noun phrase | use the documented prepositional pattern |
Quick tests
Complement-shape test
Is the reaction followed by an infinitive event, or by a noun phrase naming what caused the reaction?
If yes: Use “astonished to + verb” for the infinitive construction.
If no: Use “astonished at + noun phrase” for the named object/result.
Caveat: The two constructions are both attested; do not infer that every synonym of “astonished” takes the same complements.
Examples
I was astonished to find the room empty.
The reaction is followed by an infinitive event.
We were astonished at the result.
“At” introduces the thing that caused the reaction.
Choose the complement from the sentence structure, not by replacing one pattern word-for-word.
The evidence supports two distinct constructions.
Further guidance
Core difference
Use astonished + to-infinitive for the directly documented infinitival construction; use astonished at + 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.
- ASTONISHED — Cambridge Dictionary (opens in a new tab)Cambridge University Press & Assessment · Direct dictionary evidence for astonished + to-infinitive and astonished at + complement