register vs comprehend

register is a noun but comprehend is not a noun.

Word	Noun	Adjective	Verb	Adverb
register	Yes	No	Yes	No
comprehend	No	No	Yes	No

register (noun)	comprehend (noun)
a regulator (as a sliding plate) for regulating the flow of air into a furnace or other heating device
an air passage (usually in the floor or a wall of a room) for admitting or excluding heated air from the room
a cashbox with an adding machine to register transactions; used in shops to add up the bill
(computer science) memory device that is the part of computer memory that has a specific address and that is used to hold information of a specific kind
(music) the timbre that is characteristic of a certain range and manner of production of the human voice or of different pipe organ stops or of different musical instruments
an official written record of names or events or transactions
a book in which names and transactions are listed

register (verb)	comprehend (verb)
enter into someone's consciousness	get the meaning of something
indicate a certain reading; of gauges and instruments	to become aware of through the senses
record in a public office or in a court of law	include in scope; include as part of something broader; have as one's sphere or territory
send by registered mail
manipulate the registers of an organ
be aware of
show in one's face
record in writing; enter into a book of names or events or transactions
enroll to vote
have one's name listed as a candidate for several parties