periodical vs organ

periodical and organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
periodical	Yes	Yes	No	No
organ	Yes	No	No	No

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

Other hyponyms of periodical include digest, pictorial, serial, serial publication, series, issue, number, journal, review.

periodical (noun)	organ (noun)
a publication that appears at fixed intervals	wind instrument whose sound is produced by means of pipes arranged in sets supplied with air from a bellows and controlled from a large complex musical keyboard
	(music) an electronic simulation of a pipe organ
	a free-reeded instrument with a piano keyboard in which air is forced through the reeds by bellows
	a fully differentiated structural and functional unit in an animal that is specialized for some particular function
	a periodical that is published by a special interest group
	a government agency or instrument devoted to the performance of some specific function

periodical (adjective)	organ (adjective)
happening or recurring at regular intervals