period vs periodical

period and periodical both are nouns.

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

period (noun)	periodical (noun)
a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations	a publication that appears at fixed intervals
the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause
an amount of time
the interval taken to complete one cycle of a regularly repeating phenomenon
a unit of geological time during which a system of rocks formed
the end or completion of something
(ice hockey) one of three divisions into which play is divided in hockey games

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