Why is "world" in a phrase "the world's most beautiful flower" followed by apostrophe and s? What about "the world most beautiful flower"? Any significances?

Thank you in advance.

Question

Why is "world" in a phrase "the world's most beautiful flower" followed by apostrophe and s? What about "the world most beautiful flower"? Any significances?

Thank you in advance.

Answer

'The world most beautiful flowers' has no meaning. The apostrophe and s ('s) is there to indicate possession or belonging. They are the most beautiful flowers of the world (belonging to the world).

Answer

Good question.
The world’s most beautiful flower - The apostrophe + s shows possession. It means “the most beautiful flower in the world.” This is correct and natural.

The world most beautiful flower - This is not correct. Without the apostrophe, it sounds broken or unfinished.

So, the apostrophe + s is important because it shows that the flower belongs to the world as its most beautiful. That’s why we always say “the world’s most …” in this kind of phrase.

Answer

Maybe it would help to think of a smaller example than 'world'.  Imagine a clothing shop. The best dress in that shop would be "the shop's most beautiful dress."    "Shop's" is possessive because it's the best dress that the shop has.

Answer

It's an apostrophe of possession.

A long time ago, it would have been written like this: 
The world: its most beautiful flower.

Thus "world's" = "world: its".