postage franking vs frank

postage franking and frank both are nouns.

Word	Noun	Adjective	Verb	Adverb
postage franking	Yes	No	No	No
frank	Yes	Yes	Yes	No

As nouns, frank is a hypernym of postage franking; that is, frank is a word with a broader meaning than postage franking:

postage franking: postage stamps, or any other markings recognized and accepted by the postal system or systems providing service, which indicate the payment of sufficient fees for the class of service which the item of mail is to be or had been afforded.
frank: device or marking such as postage stamp, printed or stamped impressions, codings, labels, manuscript writings, or any other authorized form of markings affixed or applied to mails to qualify them to be postally serviced.

Other hypernyms of postage franking include franking.

postage franking (noun)	frank (noun)
postage stamps, or any other markings recognized and accepted by the postal system or systems providing service, which indicate the payment of sufficient fees for the class of service which the item of mail is to be or had been afforded.	device or marking such as postage stamp, printed or stamped impressions, codings, labels, manuscript writings, or any other authorized form of markings affixed or applied to mails to qualify them to be postally serviced.
	a smooth-textured sausage of minced beef or pork usually smoked; often served on a bread roll

postage franking (adjective)	frank (adjective)
	characterized by directness in manner or speech; without subtlety or evasion
	clearly manifest; evident

postage franking (verb)	frank (verb)
	exempt by means of an official pass or letter, as from customs or other checks
	stamp with a postmark to indicate date and time of mailing