penknife vs pocketknife

penknife and pocketknife both are nouns.

Word	Noun	Adjective	Verb	Adverb
penknife	Yes	No	No	No
pocketknife	Yes	No	No	No

As nouns, pocketknife is a hypernym of penknife; that is, pocketknife is a word with a broader meaning than penknife:

penknife: a small pocketknife; originally used to cut quill pens
pocketknife: a knife with a blade that folds into the handle; suitable for carrying in the pocket

Other hypernyms of penknife include pocket knife.

penknife (noun)	pocketknife (noun)
a small pocketknife; originally used to cut quill pens	a knife with a blade that folds into the handle; suitable for carrying in the pocket