A thing that is not required yet is purchased in great amounts anyways.
ie. a novelty

A Snuggie or otherwise utterly useless piece of consumer garbage.

\"you need a thneed\" is simply a marketing statement by the character in the book. A thneed is not REALLY needed, but is nonetheless purchased in great quantities and manufactured in great quantities to the detriment of the environment.

Something all people need. Can be 1000 different things. Also kills trees. Mr lorax disapproves.

An item, according to Dr Suess, which is most definately required.