pocketknife vs pocket knife

pocketknife and pocket knife both are nouns.

Word	Noun	Adjective	Verb	Adverb
pocketknife	Yes	No	No	No
pocket knife	Yes	No	No	No

As nouns, pocketknife and pocket knife are synonyms defined as:

pocketknife and pocket knife: a knife with a blade that folds into the handle; suitable for carrying in the pocket

pocketknife (noun)	pocket knife (noun)
a knife with a blade that folds into the handle; suitable for carrying in the pocket	a knife with a blade that folds into the handle; suitable for carrying in the pocket