rhythmical vs rhythm

rhythmical is not a noun while rhythm is a noun.

Word	Noun	Adjective	Verb	Adverb
rhythmical	No	Yes	No	No
rhythm	Yes	No	No	No

rhythmical (noun)	rhythm (noun)
	natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)
	recurring at regular intervals
	(architecture) the repetitive use of a group of visual elements to establish a recognizable pattern
	the arrangement of spoken words alternating stressed and unstressed elements
	the basic rhythmic unit in a piece of music
	an interval during which a recurring sequence of events occurs

rhythmical (adjective)	rhythm (adjective)
recurring with measured regularity