What does hypothesis mean?

Hypothesis is a more scientific method of guessing or assuming what is going to happen or how the experiment is going to turn out and why before observations and post-analyses are made. Hypothesis is just a fancy term for "pre-analysis." In laymen's terms, a hypothesis is an educated guess of what you think will most likely happen and why.

A hypothesis is what you expect will happen in an investigation. It is basically a prediction that you back up with expected science. If i was to do an investigation on whether the addition of salt to water affected the density, then my hypothesis would be that there would be a significant trend observed relating the addition of salt to the water density. A null hypothesis is a prediction which you want to disprove. Using the example above this would be: "There will be no significant affect on the density of water as salt is added" You can then say in the discussion of your results that you have shown that your null hypothesis is not true, even if you cannot get a significant quantitative result to prove your hypothesis.