offhand vs careless

offhand and careless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
offhand	No	Yes	No	Yes
careless	No	Yes	No	No

offhand (adjective)	careless (adjective)
casually thoughtless or inconsiderate	marked by lack of attention or consideration or forethought or thoroughness; not careful
with little or no preparation or forethought	effortless and unstudied
	(usually followed by `of') without due thought or consideration

offhand (adverb)	careless (adverb)
in a casually inconsiderate manner
without previous thought or preparation