So vs. Such
“So” and “such” can both intensify meaning, but their grammar differs. “So” normally modifies an adjective or adverb, while “such” introduces a noun phrase.
Use “so” before adjectives or adverbs (“so useful”); use “such” before noun phrases (“such a useful tool”).
Key details
Choose the right form
| What is being intensified? | Pattern | Decision |
|---|---|---|
| an adjective | so + adjective | Use “so” before the adjective. |
| an adverb | so + adverb | Use “so” before the adverb. |
| a noun phrase | such + noun phrase | Use “such” before the noun phrase, including “such a/an + adjective + singular noun.” |
Quick tests
Meaning / construction test
Does the intensifier directly introduce a noun phrase?
If yes: Use “such.”
If no: Use “so” when the core pattern directly intensifies an adjective or adverb.
Caveat: This is the core contrast documented by the guide; English also has additional constructions, so do not treat the shortcut as a ban on every other “so” or “such” pattern.
Examples
The instructions were so clear.
“So” directly intensifies the adjective “clear.”
She explained the process so clearly.
“So” directly intensifies the adverb “clearly.”
It was such a clear explanation.
“Such” introduces the noun phrase “a clear explanation.”
Further guidance
Adjective Boundary
Use so before an adjective or adverb when expressing degree.
Noun Phrase Boundary
Use such before a noun phrase, including patterns such as “such a good idea.”
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.
- Such or so? — English Grammar Today (opens in a new tab)Cambridge Dictionary · So before adjective/adverb phrases and such before noun phrases