Question

Can you help me define null hypothesis? I have made one and I'm not sure if it includes all the aspects of null hypothesis.

Null hypothesis is a hypothesis which states that there is no difference between the scores of two variables or an observed and a theoretical distribution. It is the statement that is tested in a test of statistical significance.

For e.g. :
I have read from random sources that it can also include the non-association of two variables.(Like the driving speed and gender are not related) But I don't completely understand that to include it in definition.