credit order vs purchase order

credit order and purchase order both are nouns.

Word	Noun	Adjective	Verb	Adverb
credit order	Yes	No	No	No
purchase order	Yes	No	No	No

As nouns, purchase order is a hypernym of credit order; that is, purchase order is a word with a broader meaning than credit order:

credit order: an order that is received without payment; requires billing at a later date
purchase order: a commercial document used to request someone to supply something in return for payment and providing specifications and quantities

Other hypernyms of credit order include order.

credit order (noun)	purchase order (noun)
an order that is received without payment; requires billing at a later date	a commercial document used to request someone to supply something in return for payment and providing specifications and quantities