packing case vs packing box

packing case and packing box both are nouns.

Word	Noun	Adjective	Verb	Adverb
packing case	Yes	No	No	No
packing box	Yes	No	No	No

As nouns, packing case and packing box are synonyms defined as:

packing case and packing box: a large crate in which goods are packed for shipment or storage

packing case (noun)	packing box (noun)
a large crate in which goods are packed for shipment or storage	a small chamber in which packing is compressed around a reciprocating shaft or piston to form a seal
	a large crate in which goods are packed for shipment or storage