This is word used to describe a characteristic of a hypothesis. it means you are able to experiment to see how two variables may be related

The most simple way how to describe a hypothesis is that this is your idea, how you think your variable (or variables) that you're observing, will react because of a certain change will be made. 

This is what a hypothesis is esentially, you can make much more complex hypothesis, or you can make multiple hypothesis. It all depends on your research question and what you're trying to find out.