Question

select the word that means an idea. wouldnt it be great if we could build an elevator to outer space? the concept of a space elevator has been around for years. however, no one has been able to make it a reality. that doesnt mean scientists arent trying, though. bradley edwards, a physicist in the united states, has been working on one since 1998. the obayashi company in japan is trying to complete such an elevator by 2050.

Explanation:

In the text, "concept" is used to mean an idea. The sentence "The concept of a space elevator has been around for years" shows that it represents the idea of a space - elevator.

Answer:

concept