serial vs semimonthly

serial and semimonthly both are nouns.

Word	Noun	Adjective	Verb	Adverb
serial	Yes	Yes	No	No
semimonthly	Yes	Yes	No	Yes

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

serial: a periodical that appears at scheduled times
semimonthly: a periodical that is published twice each month (or 24 issues per year)

Other hyponyms of serial include semiweekly, weekly, monthly, quarterly, bimonthly, biweekly.

serial (noun)	semimonthly (noun)
a serialized set of programs	a periodical that is published twice each month (or 24 issues per year)
a periodical that appears at scheduled times

serial (adjective)	semimonthly (adjective)
pertaining to or occurring in or producing a series	occurring twice a month
pertaining to or composed in serial technique
of or relating to the sequential performance of multiple operations
in regular succession without gaps

serial (adverb)	semimonthly (adverb)
	twice a month