Origin: Latin suffix -able
Unreasonable has 3 different meanings across 1 category:
not reasonable; not showing good judgment
"The unreasonable driver refused to yield at a red light, putting everyone in danger."
beyond normal limits
"excessive charges"
"a book of inordinate length"
"his dress stops just short of undue elegance"
"unreasonable demands"
Without the ability to reason; unreasoning.
"The toddler's unreasonable outburst was simply a result of his inability to reason at that age."
In plain English: Unreasonable means not making sense or being too demanding to deal with.
"His demand to pay for everything was simply unreasonable."
Usage: While often used interchangeably with illogical, unreasonable specifically implies a refusal to consider facts or compromise rather than a simple lack of logic. Avoid using it to describe someone who is merely stubborn without an underlying irrational basis.
The word unreasonable comes from Middle English, where it was formed by adding the negative prefix "un-" to "reasonable." It originally drew inspiration from a related Latin term meaning without reason or rationality.