money order vs bill of exchange

money order and bill of exchange both are nouns.

Word	Noun	Adjective	Verb	Adverb
money order	Yes	No	No	No
bill of exchange	Yes	No	No	No

As nouns, bill of exchange is a hypernym of money order; that is, bill of exchange is a word with a broader meaning than money order:

money order: a written order for the payment of a sum to a named individual; obtainable and payable at a post office
bill of exchange: a document ordering the payment of money; drawn by one person or bank on another

Other hypernyms of money order include draft, order of payment.

money order (noun)	bill of exchange (noun)
a written order for the payment of a sum to a named individual; obtainable and payable at a post office	a document ordering the payment of money; drawn by one person or bank on another