A summative modifier is a grammatical structure—usually a phrase or clause, often set off by commas—that sums up or comments on the main idea of the previous clause and then adds extra information about it.
How it works:
You write a full clause (an independent idea).
Then you add a summative modifier, which refers back to the whole idea, not just one word.
It usually begins with a noun phrase that “names” or “summarizes” the previous clause.
Common patterns:
…, this + noun phrase + …
…, a fact that + clause
…, a situation that + clause
…, something that + clause