command vs countermand

command and countermand both are nouns.

Word	Noun	Adjective	Verb	Adverb
command	Yes	No	Yes	No
countermand	Yes	No	Yes	No

As nouns, countermand is a hyponym of command; that is, countermand is a word with a more specific, narrower meaning than command:

Other hyponyms of command include order, charge, commission, direction, commandment, injunction, behest, open sesame.

command (noun)	countermand (noun)
the power or authority to command	a contrary command cancelling or reversing a previous command
availability for use
great skillfulness and knowledge of some subject or activity
an authoritative direction or instruction to do something
(computer science) a line of code written as part of a computer program
a military unit or region under the control of a single officer
a position of highest authority

command (verb)	countermand (verb)
make someone do something	cancel officially
be in command of
demand as one's due
exercise authoritative control or power over
look down on