When to use "もっと" vs "より"


Giving examples if possible, what's the difference between e.g.
[`もっと大きい`](http://eow.alc.co.jp/search?q=%E3%82%82%E3%81%A3%E3%81%A8%E5%A4%A7%E3%81%8D%E3%81%84)
and
[`より大きい`](http://eow.alc.co.jp/search?q=%E3%82%88%E3%82%8A%E5%A4%A7%E3%81%8D%E3%81%84)
to mean "more (than)"/"bigger (than)"? In what situations would you use `もっと`
over `より` and vice versa?

For instance, why or why not would the two be interchangeable in the following
sentences (example sentences from [Space ALC](http://www.alc.co.jp/)):

> 危険性がより大きい  
>  "at greater risk"
>
> それ以上である。それはもっと大きい夢である。  
>  "It is more than that; it is a bigger dream."




I'm not a native speaker, but like Chocolate says, I think もっと simply feels
more "common language", whereas より feels more fancy.

To ilustrate the range of difference, let's take your first example:

> 危険性がより大きい  
>  "at greater risk"

Now, if you used もっと, I think this translation...

> 危険性がもっと大きい  
>  "at (a) bigger risk"

...accurately illustrates the kind of difference between the two words. Not a
huge difference, but "greater" kind of sounds more eloquent than "bigger".




I'm not a native speaker, but like Chocolate says, I think もっと simply feels
more "common language", whereas より feels more fancy.

To ilustrate the range of difference, let's take your first example:

> 危険性がより大きい  
>  "at greater risk"

Now, if you used もっと, I think this translation...

> 危険性がもっと大きい  
>  "at (a) bigger risk"

...accurately illustrates the kind of difference between the two words. Not a
huge difference, but "greater" kind of sounds more eloquent than "bigger".

