casual vs irregular

casual is not a noun while irregular is a noun.

Word	Noun	Adjective	Verb	Adverb
casual	No	Yes	No	No
irregular	Yes	Yes	No	No

casual (noun)	irregular (noun)
	merchandise that has imperfections; usually sold at a reduced price without the brand name
	a member of an irregular armed force that fights a stronger force by sabotage and harassment

casual (adjective)	irregular (adjective)
hasty and without attention to detail; not thorough	contrary to rule or accepted order or general practice
not showing effort or strain	(of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement
occurring on a temporary or irregular basis	(used of the military) not belonging to or engaged in by regular army forces
marked by blithe unconcern	deviating from normal expectations; somewhat odd, strange, or abnormal
appropriate for ordinary or routine occasions	failing to meet a standard of manufacture due to an imperfection
occurring or appearing or singled out by chance	lacking continuity or regularity
natural and unstudied	not occurring at a regular rate or fixed intervals
characterized by a feeling of irresponsibility	independent in behavior or thought
without or seeming to be without plan or method; offhand	(of a surface or shape); not level or flat or symmetrical