regex to look for names in lowercase only

Hi -

I am trying to create a regex that will capture names that are only in lowercase and addresses that are only in lowercase.

So, i would match on:
henry

but not on:
hEnry

Also for address, i need to match if all the alpha characters are lower case:

So, i would match on;
123 main street

but no on:
123 Main street

Thank you