As adjectives the difference between separate and difficult
is that
separate is apart from (the rest); not connected to or attached to (anything else) while
difficult is hard, not easy, requiring much effort.
As verbs the difference between separate and difficult
is that
separate is to divide (a thing) into separate parts while
difficult is (obsolete|transitive) to make difficult; to impede; to perplex.
As a noun separate
is (usually|in the plural) anything that is sold by itself, especially an article of clothing.