What is Null hypothesis?
Also known as: H0
In statistical hypothesis testing, the assumption taken as the starting point, usually the claim that "there is no difference" or "there is no effect"; it is denoted H0. The opposing claim is called the alternative hypothesis. On the basis of sample data it is decided whether to reject or not reject H0: if the observed difference is too large to be explained by chance, H0 is rejected. Not rejecting H0 does not prove that it is true; it only means that the evidence against it is insufficient.
Source: Britannica: null hypothesis