Amanda bought a prom dress which she considered the most beautiful dress ever made.

Adjective clause:Amanda bought a prom dress

Word(s) modified:dress

No. You identified the main clause. "Dress" is part of that clause.

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The adjective clause in this sentence is "Amanda bought a prom dress." It modifies the word "dress," providing more information about it. In this case, it tells us that Amanda bought the dress.