'The world's greatest [whatever]' is subjective, but 'One of the world's greatest [whatever]s' is clearly objective. Anyway, that's why I got you this 'one of the world's greatest moms' mug!

"One Of The", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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'The world's greatest [whatever]' is subjective, but 'One of the world's greatest [whatever]s' is clearly objective. Anyway, that's why I got you this 'one of the world's greatest moms' mug!