A modifier is a word, phrase, or clause which functions as an adjective or an adverb to describe a word or make its meaning more specific. Here is a link that explains and gives examples. http://www.grammar-monster.com/glossary/modifiers_modify.htm Specifiers are shown as being of three kinds: Qualifiers, Determiners (like a, the, this, that, these, their, its, those, my, his, her, your and proper-noun possessives), and Degree Words (like too, so, very, more, most, quite). So Modifiers enhance a noun and Specifiers give possession, quantity and resemblance to a noun I hope that helps and good luck on the exam.

Well, I'm familiar with modifiers (just a little bit) but specifiers are related to generative grammar? Cause I've had only general syntax... but there is sth on my favourite website http://www.academia.edu/2724220/Specifiers_in_generative_grammar I'm not sure you'll be happy wiht this help ;)