Elevator air conditioning is fast becoming a popular concept around the world.

Nowadays, the popular concept is sustainable economic development or growth.

It is a concept popular in science fiction and fantasy works.

There would be no parole: a popular concept with politicians and the public.

A second, and less popular concept, is called a constant current method.

For some reason, this isn't a popular concept - especially here.

Beneficence to the poor is not a popular concept these days.

A popular concept is that we live in a carpentered environment.

It was the world's first five string bass guitar, a popular concept today.

It has become a very popular concept in conservation biology.