A/the world of difference
Definition 1 of 2

Context Clues
Look for words that show contrast like 'but', 'however', to understand the change 'a world of difference' indicates.

She was shy at first, but tutoring made a world of difference in her confidence.
Emphasis Added
'A world of difference' is used to emphasize an important change or distinction between things.

Working from home creates a world of difference in work-life balance.
Not Literal
The phrase is figurative and doesn't mean an actual 'world' but symbolizes an extremely noticeable difference.

Switching to LED lights has made a world of difference in our electricity bill.
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