Necessity good in the context of "Luxury good"

In economics, a luxury good (or upmarket good) is a product or item or service for which demand increases more than what is proportional as income rises, so that expenditures on the good become a more significant proportion of overall spending. Luxury goods are in contrast to necessity goods, where demand increases proportionally less than income. Whereas people consume necessity goods to meet basic survival needs, luxury goods are consumed both for their "intrinsic quality and to signal their wealth and confirm social status." In economics, luxury goods is often used synonymously with superior goods.