When something is prohibitive, it prevents you from doing what you want because the cost or difficulty is just too high. The word most often describes prices or expenses that are so extreme they stop people from buying or doing something, even if they really want to.

Imagine your class wants to take a field trip to see a space shuttle launch in Florida, but the cost of travel and hotels is $2,000 per student. That prohibitive cost means the trip simply can't happen, no matter how exciting it would be. Or consider a family that would love to buy a house near the beach, but the prohibitively expensive prices mean they'd have to spend their entire life savings and then some.

The word comes from prohibit, which means to forbid or prevent. Something prohibitive acts like an invisible barrier: technically nobody is stopping you, but the obstacle is so large it might as well be impossible. A talented student might dream of attending a particular private school, but the prohibitive tuition means their family can't afford it.

While the word usually refers to money, it can describe anything that makes something practically impossible. The prohibitive difficulty of climbing Mount Everest keeps most people from attempting it, even if they have the money and time.